I'm using tools.pingdom.com for a website page speed tester which returns 4 metrics (Perf score, Requests, Load time and Page Size).

I understand that servers may be under varying loads and therefore the score and load times may change, but I don't understand why my page size (which my site has remained unaltered between tests) should change in size.

Am I missing something here?

  • Are we talking bytes. a few KB, or real noticable differences?
    – Martijn
    May 10, 2016 at 7:23
  • It ranges from 500Kb-900Kb for the page size. I later wondered if this was the case w/ all page speed testers, but GTMetrix page speed tester remains a consistent 542kb. Retesting again w/ tools.pingdom.com and is now returning/repeating the same size now (642kb) - which is strange they're a) different sizes between the sites and b) pingdom is no longer is inconsistent with my page size. May 10, 2016 at 14:55

1 Answer 1


I would say because they request your page in a different manner. If one tester accepts gzipping, that'll result in a smaller request. Maybe one displays gzipped size, and the other the decompressed result.

Might very well be they send different request headers and because of that, get other response headers back.

  • I think gZip is an excellent guess. Could you elaborate on what you mean by sending different headers and how that might affect what comes back (presuming those headers are all referring to the same web page)? May 10, 2016 at 18:26

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