5 tools to test site load speed

Post on YSlow was one of the earliest on this blog, as well as one of the first popular posts. I still use tool extensively. It may be somewhat cumbersome for fast checks so I picked up few web-based tools for testing site load performance since then.

What tools test

Online tools of this kind download page from link you provide and log exact details about download process. Some excel at post-load analysis while other are all about exact timing of download and render.

OctaGate SiteTimer

Fast and straightforward load timer.



Hardly feature-rich but good for quick test. Has weird habit of displaying some things that have nothing to do with page like links to RSS feeds.

Link octagate.com/service/SiteTimer

Pingdom Tools Full Page Test

Also load timer type, inspired by SiteTimer according to developers.



Still no settings to play with, but has improved visualization, sorting/filtering capabilities for graph and summary result. Can optionally remember results of test.

Link tools.pingdom.com


Most complex of timers.



A lot of settings to choose – like what browser to emulate, as well as limited support for password-protected pages.

Link site-perf.com

Web Page Analyzer

Post-load analyzer.



Calculates estimated load times on different connection speeds and provides good summaries on specific performance bottlenecks.

Link websiteoptimization.com/services/analyze


Technical performance analyzer.



Allows to setup repeated tests. Generates numerous graphs, screenshots and very thorough information on all of site’s components. Creates checklist of specific optimizations with estimated size improvement.

Link webpagetest.org


I had roughly sorted test by complexity of usage and amount of insight. There is no clear winner, just try each one and decide which balance of ease of use and functions you need.

PS yes, I know this blog has some performance issues at moment. No need to try each tool on me and tell me I suck at implementing what I encourage. :)

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  • Lyndi #

    Because I write quite a few blog reviews tools like these are pretty important to me. I regularly use Pingdom Tools and Web Page Analyser. I will give the others a try. Thanks.
  • Madmouse Blog tips #

    Some interesting tools to use, now I have to figure out what all of the results mean. I think madmouseblog.com turned out pretty good.
  • Rarst #

    @Lyndi Well, those two are what I default to usually (on top of YSlow), but rest are also nice. @Squeaky Just stick to those tools that provide explanations with results. After few runs with those rest are easy to figure out because it is mostly same stuff.
  • TechZoomIn #

    I use pingdom service. But i'm getting how to reduce my load time :)
  • Rarst #

    @Lax Ehm, you are getting or missed "not" in that sentence? :) "But" confuses me, heh. Anyway I am no big expert but if you (or someone else) want me to take a look at their site load times I am more than willing to. I like figuring stuff out and site optimizing has good balance of cool but not too hard tech puzzle.
  • Donace | The Nexus #

    Sweet man; Was missing one or two will add them to my resource list ( http://thenexus.tk/free-seo-tools/ )Though yes speed is king. Will be working on site soon just to squeeze out that little bit more.
  • Rarst #

    @Donace Always glad to share some good tools. :) Here I am pretty happy with "outer" load speed but my page generation time completely sucks at moment. Need to figure out bottlenecks in database queries and cache widgets - whole different optimizing story.
  • Jonny #

    Brilliant, I use Yslow only and seem to be constantly battling to keep my site load time down. Bookmarked!
  • Rarst #

    @Jonny Glad you like it. :) YSlow is awesome but doesn't give clear picture of download process. Actually Firebug has such graph, but bit boring and hard to interpret.
  • Google Page Speed vs Yahoo YSlow | Rarst.net #

    [...] Page Speed Activity function that is similar to page load timers but provides load graphs in real [...]
  • David #

    Hi I've been trying Pingdom, Yslow and Google Pagespeed, but for similar pages, I get totally different results... It can be in the number of images, the time to load, the size of the HTTP... all the numbers are different. What is the difference between these tools for that type of calculations?
  • Rarst #

    @David What do you mean similar pages? To get close results it makes sense to test single and exactly same page. No idea on number of images. My only guess is that some tools (I think pingdom is one of them) may at times include images referenced, but not actually used in CSS. Time to load naturally varies with connection speed and quality. For YSlow and PageSpeed this would be your own Internet connection, for online tools this would be their server's. Size of elements (mostly HTML, CSS and JS) can vary because of compression used. Not all tools notice or support compression and some only report uncompressed sizes. If you provide link you are attempting to benchmark I will try to take a look. :)
  • David #

    @rarst Thanks for the quick reply. It helps a lot. This would be one of the page I am currently looking at: http://bit.ly/3xR7EQ Got a size of 207.7KB in Yslow, 123KB with Page Speed, 350KB with Pingdom Then I got between 1.8&2.4sec loadtime in Pingdom, 5.93sec with Yslow, 4.2sec with LORI (both local tools launched at the same time) I'd like to give a max. load time & size to my tech collegues and am therefore benchmarking a few sites, but really get all types of numbers... PS By similar, I meant same page, language problem, sorry :)
  • Rarst #

    @David Difference in size is definitely because of compression. Look at "Components" tab in YSlow - SIZE and GZIP columns (expand types to see gzip values). Size is what real size of component is. gzip is compressed size that is really transferred if browser supports compression (complicated topic, but modern browsers mostly do). Text resources like HTML or JavaScript code are highly compressible. So while this page is large itself and has some large scripts - it gets much smaller when compressed for transfer. Difference in load speed - as above, connection issues. Pingdom server has faster connection so faster actual load speed. Such load speed is naturally inaccurate as metric. For simple overview I suggest you use weight graphs (Statistics tab in YSlow). They show which parts of site is heavy and are easy to get. If you need range of load speeds just take site size and calculate approximate times for different connections manually, then increase a bit to account for latency of multiply components.
  • David #

    Wow! Great. A last question. How would you "manually calculate" the approximate times for the connections?
  • Rarst #

    @David So your pages weights 170KBytes. Dialup connection is 56Kbit/second = ~5KB/second, so it will take 170/5=34+lag = ~40 seconds to fully load this page. If you compare this to broadband 1Mbit/second = 128Kbyte/second it will be 170/128=1.3+lag (lower for fast connection) = ~1.5 seconds to fully load same page on such connection. This is simplification of course. There are many other factors that contribute to load speed so it's theoretical, while real page size is factual.
  • David #

    Thanks a lot for your help @rarst!
  • Rob #

    Thanks David, the tools you list will be really useful.