This is the second post of my series on assessing web performance.
- Previous post: What Metrics Matter?
This is going to be a whistle stop tour of some of the tools that are out there that will help you measure your website’s performance. This is by no means exhaustive – there are lots of other tools out there that I’m completely unaware of. If there is something you think should be added please add a comment!
This is intended for someone who is wondering “Where to start?” when it comes to performance metrics.
The four tools that I am going to mention are:
- Dev Tools “Network” tabs
- Google PageSpeed Insights
- Web Page Test
- New Relic (briefly)
Dev Tools Network tab
All of the popular browsers ship with a pretty decent set of Developer Tools these days, and they all include a “Network” tab/pane.
This should be your first stop when trying to assess page performance. It’s built into your browser, and you can test performance as you work, even on local environments. You can easily figure out how much data is needed for a page, and how many assets are being requested.
Be sure you’re aware of whether or not caching is disabled when looking at your network tab. I use Chrome, and usually have the “disable cache” option checked.
Dev Tools Network Tab Pros
- Lets you work locally
- Quick to use
- Lots of data
Dev Tools Network Tab Cons
- Only relevant to your machine and local network
- Results can vary wildly because networks are complex
Google PageSpeed Insights
Google PageSpeed Insights is an easy to use service provided by google. You give it a URL, and it gives you a score out of 100. (Actually, it gives you two scores – one for “mobile” and one for “desktop”.)
What’s more, it will give you recommendations of what you can do to increase your site’s performance.
Google PageSpeed Insights Pros
- It’s well known, and has the Google name, which stakeholders respect
- It’s simple score is easy to reference
- Bookmarkable – it will re-run the test every time you visit the result URL, so feel free to bookmark and revisit again and again
- It makes an attempt to tell you what things you can do to better your site performance
Google PageSpeed Insights Cons
- The simple score metric is a bit opaque – it’s more or less “Because Google Says So”
- It’s recommendations need to be taken kind of skeptically. They seem to be written with the assumption that every site is a single page web app. A lot of their recommendations either don’t make sense for a lot of sites, or are simply not feasible.
- There is no history – because the test gets rerun every time you visit, you can’t see what your previous score may have been. It’s up to you to keep track over time, if that’s important to you.
Web Page Test
Web Page Test is my personal favorite tool for measuring page peformance. I think that the metric that it measures is the most useful, and it gives you a lot of data. The UI design is something only a developer could love, but then again it is a power tool.
Much like PageSpeed Insights, you submit a URL for evaluation. What’s different, though, is the result of your test is a randomized URL, which you can bookmark and reference later, or send to someone.
The main metric that you will get back is called Speed Index. This is a number that you want to be as low as possible. Generally the number to shoot for is thought to be 1000.
Speed Index is a measurement of perceived performance. It is based on a visual comparison of a page over time versus when it is completely loaded. The quicker it appears complete, the lower the Speed Index. (It’s more complicated than that, but that’s the gist. A more full explanation on Speed Index can be found here.)
In addition to Speed Index you also get more fine-grained evaluations on aspects of performance like caching, compression, etc. Based on your results, there will be some recommendations made in the result report.
Web Page Test Pros
- Lots of data. Like, a lot a lot.
- Speed Index is an actually useful metric
- Lots of good recommendations
Web Page Test Cons
- The UI and Reports are something only a developer could love
- Good luck explaining what “Speed Index” is to a non-technical stakeholder
New Relic is a very popular analytics platform used to measure performance for all kinds of technology stacks. It’s used on websites, on back end servers, in mobile apps, etc.
The way it works on the web is that you include a tracking script on your page (usually in the
<head>), and it accumulates data over time, which you can monitor in lots of ways.
New Relic has various pricing tiers, so depending on how granular you want to get when digging into performance, you may have to pay for that data.
The thing that I really like about New Relic is that it measures page load time for users and averages it out. I have far more confidence in that metric as an indicator of performance when it comes to the real world, and not just me sitting at my desk.
When confronted with performance issues, stakeholders often ask how long a given asset takes to load. That’s a tough question – you can typically answer with what your Dev Tools say. But there is no way to really know that answer unless you have a service like New Relic measuring perf for users.