The rise of complex web applications and the widespread adoption of JavaScript-based server stack mean that, in some cases, the performance of some JavaScript code may affect the overall application performance. In this situation, it is imperative to analyze the performance carefully in order to come up with the right optimization strategy. There is always […]

Everyone knows that third party content can be a real problem for your website. Third party content, or 3PC, can create single points of failure (SPOF) that can drastically slow or even completely stop your webpage from loading or rendering properly. They can also be a source of unoptimized, bloated content that lowers your page […]

Let’s face it. Your business doesn’t care about web performance. Customer happiness and profits warm the business’ little corporate heart, but they need you to teach them the connection between speed and profits. The good news: web performance can make a dramatic impact on both user satisfaction and sales. But you still need to prove […]

React is a JavaScript library for building user interfaces developed by Facebook. It has been designed from the ground up with performance in mind. In this article I will present how the diff algorithm and rendering work in React so you can optimize your own apps.

Probably many – if not most – of us speed freaks work for big companies that are optimizing top 1,000 websites. Some companies have the budgets to hire people who work on WPO full time. Those companies are able to do that thanks to huge revenues – otherwise it would not be Shampoos Clearly sore […]

Responsive Web Design (RWD) is now a well established technique yet it’s adoption is still surprisingly low. Guy Podjarny’s recent research shows that only one in eight websites is responsive. Often when responsive sites are designed the approach is primarily from a visual design perspective and teams struggle with the complexity of changing design and […]

A solid engineering mindset is key to successful performance optimization. This has been driven into me by the wisdom of engineers such as Bharat Mediratta, Darin Fisher, James Simonsen, Nat Duca, Pat Meenan, Simon Hatch and Steve Souders (to name a few), as well as by trial-and-error during almost 10 years of performance work. As […]

When working on web performance we often spend a lot of our time staring at resource waterfalls to identify issues with sites. There is a lot you can tell without having to look to closely and most of the key issues with a page will be identifiable from even just looking at the thumbnail view […]

Most mobile carriers force all HTTP traffic to go through their proxies that—among other things—recompress images on the fly. This means that visitors of your website or mobile app may be getting images in much lower quality than you’re serving. I’ve decided to have a closer look at what exactly these proxies do to images […]

It goes by many names – some call it the preload scanner, others the speculative parser or the look-ahead downloader. Its tales are often passed from senior Web developers to junior ones when the day turns to night and their Web site's resource loading order makes very little sense: "Have you heard of the preloader? […]

I have been doing a lot of work this year about creating a performance culture within a company. This is an essential step on the route to creating good performance in your products and only when you start treating performance as a first class citizen will you start to get buy in to the time […]

Behind every device connected to the internet there is an underlying network, which dictates the route data packets travel. When an end user goes to www.google.com from his smartphone, the physical route and limitations of a mobile network compared to consumer internet service providers are rather hidden. Latency offers a way to shed light on […]

In last years Performance Calendar Marcel Duran told us how to make Proactive Web Performance Optimization, meaning how can we make sure our sites are as fast as possible before a new version is released. In this year calendar Maciej Brencz showed us how to integrate phantomas in your continuous integration. And earlier this year […]

A couple of weeks ago, our VP Acceleration, Kent Alstad, delivered a great session at DevCon5. Among other things, Kent said: “If a site is slow, people think it’s broken. A slow website damages your brand.” This is a profound truth about performance. When pages are slow, people don’t put their negative feelings about that […]

I recently had the pleasure to listen to Ilya Grigorik give a talk at Velocity in NYC on Breaking the 1000ms Mobile Barrier. During the talk, Ilya used PageSpeed Insights to demonstrate that several high profile websites had overlooked some very simple and common optimizations and resulted in poor PageSpeed scores. For the unfamiliar, Pagespeed […]

Most performance advice today centers around Page Load Time (PLT) and this is, of course, critically important to success. We reduce or remove requests, compress our assets and minify JavaScript and CSS. It’s all good stuff, but it’s only part of the picture. The majority of the time a user spends on your site is […]

It’s common knowledge that domain sharding, where the resources in a web page are shared across different domains (or subdomains), is a good thing. It’s a good thing because browsers limit the number of connections per domain: splitting a web page across domains means more connections and hence faster page downloads. Overall domain sharding results […]

“Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about Hands s destroy with, . Have Anxiety oline pharma store most using problem clean process […]

The world of web development is strikingly different today than it was when I started my career. Today, you don’t usually need to argue for performance, everyone knows that it’s important. Through efforts like Velocity, the Performance Advent calendar, and local performance meetups, the word has gotten out loud and clear: performance matters. It matters […]

Someone on Twitter recently asked aloud whose responsibility performance was. A few of the responses quickly said “the developers”. This is a typical mindset, but a fundamentally flawed one. Performance is not just a developmental concern, it’s a fundamental component of the user experience. Our relationship with pages and applications online are made up of […]

Being a web techie today means being bombarded with new information. Technology is moving at a ridiculous pace, and just staying up to speed is probably a full time job. This challenge also applies specifically to the world of web performance. In the last 2-3 years, we’ve seen dozens of new browser capabilities, a myriad […]

In case any browser teams are awash in the spirit of holiday gift-giving, here’s my wishlist for performance features I’d love to see. I did a similar Browser Performance Wishlist in 2010. I hope this list will initiate numerous discussions that result in a faster browsing experience for everyone. Navigation Timing in Safari async 3rd […]

At the dawn of the mobile app economy, just having a presence in the various app stores was enough to ensure success. However, as the number of applications has exploded, the number of apps competing for your customers has increased. It is now important to differentiate your application from your competition. Performance of your mobile […]

When people talk about end-to-end performance, they usually mean one dimension of performance: performance observed by end-user (from sending a request until getting full response). But without considering other dimensions of performance – such as load or data – such view is rather limited (although, as any model, is useful in many cases). Another dimension […]

Domain sharding has long been considered a best practice for pages with lots of images.  The number of domains that you should shard across depends on how many HTTP requests the page makes, how many connections the client makes to each domain, and the available bandwidth.  Since it can be challenging to change this dynamically (and […]

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Dec 2013

Year on year, the weight of our web pages is gradually increasing. As web developers, we all know the impact that heavier web pages can have on page load times; they increase the amount of time that our users need to wait, which results in a poor experience. This gradual growth in page size is […]

tl;dr WebP and JPEG XR are two useful new image formats supported by only some browsers. Both provide good compression and add valuable support for lossy compression with transparency. Today it takes some effort to serve the right images to the right browsers. Tools for creating and working with WebP images are much better than […]

Web performance is gaining interest in IT world since 2010. There are many tools that can help you in making and keeping your site fast. Google’s PageSpeed, YSlow and WebPagetest to name just a few of them. But what if you want to run these tools regularly (as a part of Continuous Integration) or get […]

The task that Nathan LeClaire bombed during his interview is only one of many common situations that could be improved on the internet we surf these days. Unfortunately, those situations are rarely described or resolved in daily tutorials and even most common books, so here one approach with multiple possible purposes. More Than Just Asynchronous […]

What is your Mobile Strategy? A.”We don’t have one” B.”We swear on responsive web design” C.”We take mobile very seriously and have dedicated sites”. If you’ve answered B or C, read on…

Web performance is number one complaint our users have. We may have accepted that web sites are slower than installed apps that have all the data they need on the hard drive. You know, network and all. But it would appear that our users have not accepted this as a fact.