Advanced Web Worker Performance

This post offers some advanced considerations on the mechanics of squeezing the best performance possible out of workers. I only mention a few (very) rough benchmarks since the goal is to focus on guidelines and food-for-thought, rather than specifics. It’s also fair to say that not all tasks benefit from using web workers. The best way to know is to test performance with and without the workers.

Processing costs. There are a variety of costs associated with manipulating data. Manipulating data means any task you run against it such as looping, converting, parsing and analyzing. Each one of these tasks should be evaluated for the cost in terms of CPU usage and time spent. By looking at these aspects, you can determine the benefits of having a web worker versus not having a web worker.

Pre-processing – manipulating data before sending it to the web worker.
Peri-processing – manipulating data while doing work on the background thread.
Post-processing – manipulating data after it’s been received back from the web worker.
Total processing – this benchmarks the processing from the very beginning until the very end.

Time stamp before and after each process that handles data. Tools such as console.time are invaluable in identifying actual and potential bottlenecks. Also make liberal use of the developer tools such as Chrome’s CPU profiler that now includes screen captures.

Total CPU and memory usage. There’s often a misperception that just because CPU usage has been outsourced to the background thread that it won’t negatively impact an application or contribute to jank. This is not true, especially on mobile devices that are already CPU and memory constrained. CPU headroom, or the amount available for application processing, is finite and typically doesn’t care whether CPU is used on the main thread or a background thread.

Web apps are wholly dependent on how each browser vendor uses CPUs and manages threads behind the scenes for every browser version and operating system. Using JavaScript you cannot guarantee how the browser will spread CPU load across cores.

In fact, I’ve seen web worker performance improvements made in Chrome that create almost an exact opposite performance decrease in Safari! Talk about a WTF moment.

Cloning costs. Careful consideration should be placed on the costs associated with the act of sending and receiving messages. Sending and receiving isn’t “free”, in fact the amount of CPU consumed can directly cause jank.

Web workers use a cloning algorithm for serializing objects that go in and back out, and cloning uses CPU cycles. Yes, even if you are using transferable objects there may still be performance implications especially when dealing with large amounts of data (>100MBs) as well as on mobile devices. You simply will never know unless you test, test, test.

In some cases, the cloning costs related to both sending and receiving messages may outweigh the performance benefit of using a web worker. If the entire round-trip time and CPU utilization is greater than simply keeping the processing on the main thread – then you probably don’t need a web worker.

Pooled workers. Should you use one worker or several? The only reliable way to know is to experiment. One approach to eke out greater performance is to create a pool of workers. The concept is a task that can be broken up and passed on into smaller concurrent worker tasks and then reassembled after all tasks have completed.

Here’s an example application that retrieves a GeoJSON file, parses it, then displays the data on a map. Open up the developer console and run each application multiple times. You can also download and experiment when this application yourself with increasing and decreasing the size of the thread pool:

Example 1: Parsing using no web workers
Example 2: Parsing using one web workers
Example 3: Parsing using two web workers

With respect to binary versus non-binary data, I’ve seen diminishing returns when using larger number of workers with JSON files. On the other hand, there are a number of posts on the web that show great performance processing image data with increasing numbers of workers.

This also may be dependent on the browsers-threading model and how it uses the number of cores on your device or laptop. How do you know? Test and benchmark.

Re-use workers, or re-create for each loop? There are costs associated with initializing workers. Depending on the type of application, it may benefit you to re-use workers rather than re-create them for each loop. This depends on how complex your web workers are, how many you need to spin up, the type of device they are running on and how often you are using them.

Some applications may run on a timer once every 5 minutes. If that’s the case does it make sense to keep workers sitting unused in memory for that long? Maybe or maybe not. Other applications may only need the workers at startup and there’s definitely no need to keep them around after that. The list of use cases are endless.

Here’s some very rough test results on the time to simply initialize web workers. This example used identical workers that contained 67 lines of code:

Macbook Pro: 2 workers, 0.4 milliseconds on average
Macbook Pro: 4 workers, 0.6 milliseconds on average
Nexus 5: 2 workers, 6 milliseconds on average
Nexus 5: 4 workers, 15 milliseconds on average (border-line UI jank)

As far as computational horsepower, the Macbook used in the tests had 2.6 GHz i7 with 16GB of 1600 MHz DDR3. The Nexus 5 had a Snapdragon 2.26 GHz with 2GB of 800 MHz RAM. Clearly the Macbook outclasses the Nexus. It’s important to note how much longer it took to spin up a pool of workers on a mobile device. That’s an example of an app that would work seamlessly on a powerful laptop, but could produce jank on a mobile device.

Closing Notes. Web workers are fairly straight forward to bolt into an application, but tuning them up to gain the true performance benefits can be a bit more tricky. With a little exploration and experimentation, workers can potentially provide huge benefits for your application’s performance.

Sample Application

[Fixed broken links: July 7, 2016]

You can’t just wrap old websites in bootstrap and call it a day

Just because you wrapped an existing website in bootstrap doesn’t necessarily mean it’s ready for use on mobile devices. This is especially true if the website was originally designed for desktop browsers. Yes, bootstrap can significantly improve the user interface and make it flexible across multiple screen sizes. But it’s also up to you to roll up your sleeves and make sure the code behind the scenes is also worthy of being mobile-ready.

So, here are a three challenges to consider that will help keep your smartphone using visitors happy.

Challenge 1 – The internet connection on mobile devices is not as reliable as your home or office wired network. That’s a fact. Download speeds can and will vary significantly. The larger the website in MBs, the more links it has to download, the more non-optimized images then the longer it will take to render and become ready for use, especially on a mobile device. And mobile users are a very impatient bunch when it comes to sluggishness.

Size does matter with web sites. Smaller sized files download faster. The fewer number of files that make up a website also means faster downloads. Optimize, optimize and optimize some more. Minify files. Combine multiple files into one. Optimize images for web display.

Challenge 2 – Site navigation needs to be rethought and resized with mobile users in mind. Modern mobile devices use finger-based navigation, as opposed to high-precision mouse pointers. Teeny, tiny buttons or links that look cool on an ultra-high resolution MacBook retina screen positively suck when you are trying multiple times to click on them with your fingertip. On some websites using desktop navigational elements on your phone becomes like a macabre video game as you repeatedly play hit-or-miss with your fingertips.

Mobile websites should be finger lickin’ good. Okay, maybe you don’t really have to lick your fingers, but at least right size your navigational elements while keeping people’s fingers in mind. And fingers come in all shapes, sizes and levels of dexterity. Bootstrap can help with this.

Furthermore, your design and testing should work equally well in both portrait and landscape modes (phone right side up or phone on its side), and you should be able to switch back and forth seamless between the two modes in the same browser session.

Challenge 3 – Mobile devices are significantly more sensitive to browser memory leaks and bloated web pages. The mobile operating system will simply kill of any app that it deems to be using too much memory. And most of us are simply not good stewards at keeping our mobile browsers tuned up and happy. Browser caches grow huge and don’t get cleaned out regularly; we keep too many tabs open and probably have more information in our browser history than the library of congress. To further add to our woes, many of us let our phones run for weeks without a restart which can allow memory leakage to grow over time.

Tweak as many aspects of web page performance that your time will allow. Optimize old code by re-writing and striving to add new efficiencies. I know it may sound crazy, but if your site is particularly large and complex then consider creating focused, mobile-only sites that have scaled down content, rather than trying the one-size fits all approach. Smaller sites not only load faster but they are easier to navigate, take up less memory and typically perform better.

Fastest way to find an item in a JavaScript Array

There are many different ways to find an item in a JavaScript array. With a little bit of testing and tinkering, I found some methodologies were faster than others by close to 200%!

I’ve been doing some performance tweaking on a very CPU intensive JavaScript application and I needed really fast in-memory searching on a temporary array before writing that data to IndexedDB. So I did some testing to decide on an approach with the best search times. My objective was to coax out every last micro-ounce of performance. The tests were completed using a pure JavaScript methodology, and no third party libraries were used, so that I could see exactly what was going on in the code.

I looked at five ways to parse what I’ll call a static Array. This is an array that once it is written you aren’t going to add anything new too it, you simply access its data as needed and when you are done you delete it.

  1. Seek. Create an index Array based exactly on the primary Array. It only contains names or unique ids in the same exact order as the primary. Then search for indexArray.indexOf(“some unique id”) and apply that integer against the primary Array, for example primaryArray[17] to get your result. If this doesn’t make sense take a look at code in my JSFiddle.
  2. Loop. Loop thru every element until I find the matching item, then break out of the loop. This pattern should be the most familiar to everyone.
  3. Filter. Use Array.prototype.filter.
  4. Some. Use Array.prototype.Some.
  5. Object. Create an Object and access it’s key/value pairs directly using an Object pattern such as parsedImage.image1 or parseImage[“image1”]. It’s not an Array, per se, but it works with the static access pattern that I need.

I used the Performance Interface to get high precision, sub-millisecond numbers needed for this test. Note, this Interface only works on Chrome 20 and 24+, Firefox 15+ and IE 10. It won’t run on Safari or Chrome on iOS. I bolted in a shim so you can also run these tests on your iPad or iPhone.

My JSFiddle app creates an Array containing many base64 images and then loops thru runs hundreds of tests against it using the five approaches. It performs a random seek on the Array, or Object during each iteration. The offers a better reflection of how the array parse algorithm would work under production conditions. After the loops are finished, it then spits out an average completion time for each approaches.

The results are very interesting in terms of which approach is more efficient. Now, I understand in a typical application you might only loop an Array a few times. In those cases a tenth or even hundredth of a millisecond may not really matter. However if you are doing hundreds or even thousands of manipulations repetitively, then having the most efficient algorithm will start to pay off for your app performance.

Here are some of the test results based on 300 random array seeks against a decent size array that contained 300 elements. It’s actually the same base64 image copied into all 300 elements. You can tweak the JSFiddle and experiment with different size arrays and number of test loops. I saw similar performance between Firefox 29 and Chrome 34 on my MacBook Pro as well as on Windows. Approach #1 SEEK seems to be consistently the fastest on Arrays and Object is by far the fastest of any of the approaches:

OBJECT Average 0.0005933333522989415* (Fastest.~191% less time than LOOP)
SEEK Average 0.0012766665895469487 (181% less time than LOOP)
SOME Average 0.010226666696932321
FILTER Average 0.019943333354603965
LOOP Average 0.02598666658741422 (Slowest)


OBJECT Average 0.0006066666883028423* (Fastest.~191% less time than slowest)
SEEK Average 0.0012900000368244945 (181% less time than LOOP)
SOME Average 0.012076666820018242
FILTER Average 0.020773333349303962
LOOP Average 0.026383333122745777 (Slowest)

As for testing on Android, I used my Android Nexus 4 running 4.4.2. It’s interesting to note that the OBJECT approach was still the fastest, however the LOOP approach (Approach #2) was consistently dead last.

On my iPad 3 Retina using both Safari and Chrome, the OBJECT approach was also the fastest, however the FILTER (Approach #3) seemed to come in dead last.

I wasn’t able to test this on IE 10 at the time I wrote this post and ran out of time.


Some folks have blogged that you should never use Arrays for associative search. I think this depends on exactly what you need to do with the array, for example if you need to do things like slice(), shift() or pop() then sticking to an Array structure will make your life easier. For my requirements where I’m using a static Array pattern, it looks like using the Object pattern has a significant performance advantage. If you do need an actual Array then the SEEK pattern was a close second in terms of speed.


JSFiddle Array Parse tests
Performance Interface

[Updated: May 18, 16:06, fixed incorrect info]

Debunking the myth of the one second web page load rule

Ever since Google announced that every mobile web site had to achieve less than one second loading times, I’ve been meaning to do a fun, psuedo-scientific study to help start the discussion of putting this well intentioned goal into a perspective that everyday developers and businesses can understand. This topic has been heavily promoted, with most of the blog posts simply trumpeting agreement and either implying or coming right and saying that any page that loads over one second is pretty much worthless. In case you’ve never read the actual article, here’s a qoute from Google:

“we must deliver and render the above the fold (ATF) content in under one second, which allows the user to begin interacting with the page as soon as possible.”

I propose that most consumers will put up with a majority of sites that don’t deliver in exactly one second as long as the following general criteria are met: the user finds what they want or need the majority of the time, the user interface is fairly easy-to-use and intuitive, that there are limited or no overbearing advertisement banners (whoops!), and that the page loads within a reasonable amount of time. I really haven’t done enough research to know what a ‘reasonable amount of time’ is, but I know from testing that very few sites today deliver true sub-second performance. So let’s tear into this a bit.

First don’t get me wrong, I think sub-second performance is a very worthy goal and I absolutely think every web developer worth his or her salt should strive as hard as they can to make their web page performance as fast as possible. Reality is that budgets can be limited, time frames for deliverables can be short and not everyone is a website performance expert. However…I think we need to start asking some hard questions to make sense of the one-second rule and understand how it can be applied in our everyday development work rather than simply taking it at face value, for example:

  • What industries in particular does the rule apply? I suspect it’s mostly applied to the online retail industry. I think web site visitors cut other industries a reasonable amount of slack.
  • Does the rule only apply to first time visitors?
  • Do repeat visitors abide by other page speed rules? Repeat visitors can take advantage of cached browser pages to speed up their viewing experience
  • How do lousy mobile internet connections factor into this equation? For example, if someone knows they have a lousy internet connection most of the time do they factor that into their online buying decisions?
  • Does the rule apply to all countries or just the U.S.?
  • What is the ideal internet connection speed that this rule is based on? It seems unlikely that a page would have to load under one second regardless of the connection speed.
  • Does this apply to only self-hosted websites? What if your website is hosted on Amazon Webstore or Etsy because with these sites you don’t really have any control over how their webservers, DNS, cloud or internet pipe are configured.

I then went about verifying who are the largest online retailers in the U.S. by sheer sales volume and I came up with Amazon, Staples, Apple and Walmart as good candidates for the top four. However you verify this list, we can all agree that these four sites generate a massive amount of internet traffic, billions of dollars in revenue per year and perhaps even a majority share of internet sales. Given the fact that these stores are were tens of millions of people successfully shop every day I wanted to use the seemingly undisputable shopping experience of these retailers as a basis for comparison.

It seems like a fair assumption that these retailers must be doing something right, and therefore whatever they are doing could be a potential guideline for others. I theorize people’s online shopping and surfing expectations are formed by the websites on which they shop the most. You tend to do in-store shopping at places where you are comfortable and that the same can be said for on-line shopping. Therefore, we need to understand these leading retailers performance baselines to get some basic numbers that we can compare our against our own websites performance.

The Device

For my device, I used my middle of the pack Nexus 4 on a DSL WiFi to ensure the best possible consistent connection. Where I live 4G speeds can fluctuate quite a bit during the day, so in order to normalize those issues out of the tests I simply went with WiFi:

Android Nexus 4, Android v4.4.2
Native Chrome browser
12 Mb/sec DSL/WiFi via G Band (verified between 10 – 12 Mb/sec) – Your own WiFi experience will vary significantly.

To measure performance, I used the latest desktop version of Chrome Canary and it’s new mobile inspection tools that were hooked up to my phone via USB cable. This works really, really well, by the way.

The Criteria

Here is what I was looking for. Your test results will vary based on your device, other applications running and internet connection speeds. I didn’t test iTunes because, well, I don’t use iTunes on my Android and it’s not a website. Believe it or not, when I went to on my Android I got a desktop website and not a mobile website.

I chose the following criteria to put context around the very first page load, since that’s what Google seems to focus on the most. My goal was to load each page two times. First time is with an empty browser cache and second time is with the website cached in the browser. Then I repeat the tests multiple times to help account for any anomalies.

Here’s the criteria I looked  at:

  • Page lag with the browser cache empty. This represents a first time page visitor. By the way, I’m making a distinction between the technical time that Chrome Devtools reports the page has loaded and when the various parts and pieces within a web page finish spinning up first. This may result in a slight delay until you can actually start navigating around. This is a very subject number and it’s really hard to eyeball it accurately, but we’ve all experienced it. A web page can ‘appear’ to look like it has loaded however when you go to scroll the page down nothing may happen for a short period of time. I fully acknowledge that some of my perceived delays are due to the lag time looking back and forth between a timer and the web page which were right next to each other.
  • Page lag with web page cached. I report both the technical page load time and the perceived page load time. This represents a repeat visitor.
  • Total download time with no cache. This is the time in which all HTML, JavaScript and CSS has finished loading. As mentioned in bullet 1 this represents the number reported by the developer tools. Lazily loaded content can continue to happen unbeknownst the to user and drag down page performance for the first time page visitor.
  • Total download time with cache. Lazily loaded content can also drag down page performance for repeat visitors.
  • And last but not least, Google’s PageSpeed Insights online tool gives a few guidelines for trying to examine how well a website page stacks up against specific criteria. My only sticking point is it’s not 100% clear what criteria is being used. But, I will point out that not a single top four website got excellent ratings in the ‘speed’ category. In fact, if we were giving out grades, two of them were in the ‘C’ category and the other two were in the ‘F’ category. Tests (Averaged)

  1. Page lag no cache – 1.18 seconds reported, however based on my perception it looked more like between 2 and 3 seconds as the page finished visually loading.
  2. Page lag cached – 1.53 seconds according to Chrome dev tools. Strangely, the cached page tests seemed just a hair slower than the non-cached page. I’ve noticed that browsers can sometimes be a bit slow when grabbing cached files. It would take more research to dig into how they construct their page and what cached settings are used.
  3. Total download time (no cache) 36.52 seconds, 819KB, 103 requests (Yes, that’s right…around 35 – 36 seconds for a full and complete page load)
  4. Total download time (cached) 4.59 seconds, 428KB, 78 requests
  5. PageSpeed Insights
    1. Speed – 71/100
    2. User Experience – 99/100 Tests (Averaged)

  1. Page lag no cache – 415ms reported, based on my perception it looked more like between 1 and 3 seconds as the page finished visually loading. There was a somewhat brief spinner icon that displayed as the page loaded. Fast!
  2. Page lag cached – 378ms actual, based on my perception it looked more like between 1 and 2 seconds. I was able to start scrollable immediately.
  3. Total download time (no cache) 10.32 seconds, 358KB, 41 requests
  4. Total download time (cached) 9.61 seconds, 47KB, 30 requests
  5. PageSpeed Insights
    1. Speed – 77/100 (This number surprised me, but again we don’t know how the number was calculated)
    2. User Experience – 99/100 Tests (Averaged)

  1. Page lag no cache – 5.52 seconds reported, and that approximately matched what I could see.
  2. Page lag cached – 4.45 actual and that also matched what I could see.
  3. Total download time (no cache) 8.25 seconds, 572KB, 44 requests
  4. Total download time (cached) 7.04 seconds, 25KB, 39 requests. Wow, 7 seconds for 25KBs??
  5. PageSpeed Insights
    1. Speed – 50/100 (Yikes!)
    2. User Experience – 96/100 Tests (Averaged)

Apple gets the worse grade of the group because when I surfed to I got a full blown desktop website instead of a mobile-enabled website. PageSpeed Insights apparently agreed with me.

  1. Page lag no cache – 2.41 seconds reported, and my eyeballing it said between 2 and 4 seconds.
  2. Page lag cached – 1.69 seconds according to Chrome dev tools. My eyeballing it tended to look like around 2 seconds.
  3. Total download time (no cache) 3.66 seconds, 2.8MBs, 72 requests.
  4. Total download time (cached) 2.46 seconds, 905KB, 71 requests.
  5. PageSpeed Insights
    1. Speed – 58/100 (Yikes!)
    2. User Experience – 60/100 (Double Yikes!)


Since the vast majority of internet users buy products from these major retails, I believe their overall perceptions of how a web site should perform is in a great part established by their experiences while buying products online from them. None of the top sites were perfect, and there is always room for continued improvements.

Only one website out of the top four Internet retailers delivered a technical page load speed that was under one second: Amazon came really, really close. Staples had mediocre mobile performance. Apple didn’t offer my Android phone a mobile-enabled website.

There is a difference between the times when the page is loaded in the browser as reported by the developer tools and when all web page components become completely visible and then a short time later, ranging from several hundred to several thousand milliseconds, fully usable. As a mobile web developer I can tell you it takes a bit of time for a mobile application to be 100% ready. Many (most?) of us have experienced the often herky-jerky surfing experience as a web page bounces up and down while the content is still loading in the background. iPads have this nasty habit if you aren’t patient enough to wait and wait until the page “appears” to have finished loading. Because of this experience, defining technically at what point the page becomes fully usable can be fairly subjective. This is especially true because some retails treat tablets like desktop machines and deliver a full blown version of a website. Testing for when the page becomes visible and usable is very dependent on the phone’s capabilities, any other applications that might be using the phones hardware and bandwidth resources, as well as the internet connection at that point in time and the users perceptions!

Repeat page visits almost always load faster. Web developers would already know this, but it’s important to keep in mind for making sense of page performance discussions: first time visitors will get a different experience than repeat visitors who come back frequentyly. There is all sort of magic that can be done to control and tweak page caching.


Mobile Analysis in PageSpeed Insights
Mobile Path to Purchase: Five Key Findings (interesting info on how people use mobile for retail)
Amazon’s sales versus others (WSJ)
Top 5 largest online retailers (

The 3 most important questions for building a successful website

I’ve lost count of the number of times I’ve been told by web development teams that a public facing web site must be okay because there haven’t been any (or many) complaints. True story. Okay…sure, that is one way to measure success. But now that I’ve called this out, most of you will likely agree this shouldn’t be the first metric you look at.

Websites need to be looked at through the lens of our users. I think people take things personally when they visit a website. Web surfers form expectations based on all the other sites they visit as they go about their day, it’s not just about your website. If you want them to come back often, they need to like using your website. It’s similar to anything else in life. If it’s frustrating to do something then you’re not likely to keep doing it over again for very long.

An excellent website that fosters long term loyalty will easily answer three questions:

  1. How easy is it to find what I want?
  2. How long did I have to wait for the pages to load?
  3. Did the website work on my particular device?

You may, in fact, have the most awesome, beautiful GPU intensive website ever built. However, if people can’t find what they want or if they have to wait too long to get it, or it just didn’t work on their device of choice then you’ve lost them. For example, if you are monitoring your website stats and notice a shift from iOS-based devices to Android, then you’d better make sure your website works on Chrome.

Certainly there are many, many other questions to be asked when building an excellent website and, of course, I’m oversimplifying things quite a bit. But the nice thing about these three questions is you can always swing the conversation back to them. Use can use these as a tuning fork to help build a solid foundation for success.

I think we can all take lessons from 3rd party travel websites. These websites operate on thin margins and they have to do only one thing to be successful: sell as many travel packages as possible. There is one thing that is absolutely consistent across the successful travel sites: the primary call to action is always in the upper left hand corner and it asks the three most important questions right up front. What’s your starting point? Where are you going? How do you want to get there? Bam.

Smartphone devs, yes SD card speed matters!

If you want to get the highest performance out of your SD cards then read on. The purpose of this article is to raise awareness and spark your curiosity about SD card performance considerations.

Micro SD Class 2

Many developers I talk to aren’t aware that the read/write speeds of SD memory cards can have a significant affect on performance. This is especially true if you are moving around lots of data between a smartphone and the SD card. The good news is there is quite a bit of information out there to help you maximize performance, and a lot of it comes from high-end, camera aficionados believe it or not.

The most common feedback I get is developers typically buy cards with the most capacity at the lowest price. Depending on what you are doing, cheapest and slower isn’t always better. With little bit of research your read/write performance could get significantly better.

To start with there are four common speed classes: 2, 4, 6 and 10 and they represent an approximate minimum performance rating. You can find this number on the front of your card:

  • Class 2 ~ 2 Mbytes/sec
  • Class 4 ~ 4 Mbytes/sec
  • Class 6 ~ 6 Mbytes/sec
  • Class 10 ~ 10 Mbytes/sec

Read/write performance to your phones SD card really depends on HOW your application reads and writes data. You may have to do some testing to find out what works best. It depends on the consideration of multiple factors including:

  • Typical file types (e.g. video vs. text vs. image, etc)
  • Average file or data transaction size
  • Percentage of reads to writes
  • Duty cycle (percentage of reads or writes over a fixed time period)
  • Usage pattern

Usage pattern deserves a bit more attention and really starts to tell the story of what your application does behind-the-scenes. I think the best way to describe it is through some common use cases:

  • Many small reads and writes to/from a local database.
  • Occasional small reads and writes to local database.
  • Occasional large reads from local database.
  • Occasional large reads and writes to/from local database.
  • Large read upon application startup and large write upon application shutdown.

Wikipedia has noted that speed can differ significantly depending on what you are writing to the card. The article notes that writing large files versus writing many small files has widely different affects on performance. I’d seen similar observations when I worked on ultra-high performance server systems. So, the concept still remains today and provides excellent hints on how to tweak every extra millisecond of user experience.

If you need maximum performance then consider reformatting or defragging your card on a regular basis. I know Windows disk defragmenter utilities work on most SD cards, not sure about Mac. I have also seen multiple articles talk about bigger capacity is better because of memory fragmentation. With memory fragmentation, the card speed starts to decrease over time as the data becomes more fragmented. It’s the same concept as when you “defrag” the hard drive on your laptop.


If you want to learn more here are some helpful links:

SD Association – Bus speed

SD Association – Speed Class

Wikipedia – Secure Digital (See Speed Class Rating section)

Does your camera need a fast SD card? (good insight into SD card speed)