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WebPageTest is a web performance testing tool, now owned by Catchpoint, that runs pages in real browsers from real locations and produces detailed waterfalls, filmstrips, and metrics.
We're honest. WebPageTest is a great tool with real advantages — pick the one that fits your workflow.
This is a comparison between two tools that mostly do different jobs, and pretending otherwise would be dishonest. WebPageTest is a performance laboratory. It loads a specific page in a real browser, from a real location, on a configurable connection, and reports exactly what happened: every request in a waterfall, every visual change in a filmstrip, every metric from first byte to Core Web Vitals. It has been the reference tool for web performance engineers for the better part of two decades and, under Catchpoint, remains free for core testing with paid API plans for automation and scale. SlapMyWeb is a website audit platform. Performance — including Core Web Vitals — is one of its eleven pillars, alongside crawlability, on-page SEO, content, links, mobile UX, structured data, international SEO, authority, SERP, and AI search readiness, plus accessibility and security modules. Where the two overlap is the performance pillar; where they diverge is everything else. The real question for most readers isn't which tool wins, but which job they're hiring for — and whether the honest answer is both.
On performance specifically, WebPageTest is deeper, and it isn't close. Scripted multi-step journeys, custom metrics, traffic shaping, device-level testing from dozens of locations, side-by-side comparisons, and frame-by-frame filmstrips give an engineer everything needed to explain why a page is slow at the network and rendering level. SlapMyWeb measures performance and Core Web Vitals as part of its scan and flags concrete problems — compression, render-blocking resources, image issues — but it does not attempt waterfall-level forensics. On everything that isn't load performance, the situation reverses. WebPageTest does not audit titles and meta tags, content quality, internal linking, structured data, hreflang, accessibility, or AI search visibility, because that was never its job. SlapMyWeb's 240+ checks cover all of it, with an AI layer that converts findings into a plain-English verdict, a prioritized plan, and generated fix code. Output style is the other meaningful difference: WebPageTest's results assume a technical reader; SlapMyWeb's are written so a marketer or client can act on them without a performance engineer interpreting.
WebPageTest's core testing is free, which for a tool of its depth is remarkable and a large part of why it's beloved. Catchpoint monetizes through paid plans for API access, higher test volumes, and integration into monitoring workflows — relevant mainly to teams automating performance testing in CI or at scale. SlapMyWeb's free tier offers 3 anonymous scans a day with no signup and 10 scans a day on a free account, each returning the full issue list with a branded PDF and 30-day history. Paid tiers buy workflow breadth rather than basic access: $9/mo Pro adds full fix code, keyword research, and rank tracking; $29/mo Agency adds white-label, multi-client workspaces, bulk scans, and backlinks; $99/mo Enterprise adds API and webhooks. Comparing prices directly is slightly artificial because the products monetize different things — WebPageTest charges for automation at scale, SlapMyWeb for SEO workflow features. The practical takeaway: a developer can use both free tiers indefinitely for manual work, and what you'd pay for differs by role — performance automation budget goes to Catchpoint, SEO and client-reporting budget goes to SlapMyWeb.
WebPageTest serves performance engineers, front-end developers, and technically inclined SEOs who need to diagnose why a page is slow — not just that it is. If your work involves debugging a layout shift, comparing CDN configurations, validating a third-party script's impact, or measuring an optimization before release, WebPageTest is the right instrument and SlapMyWeb is not a substitute. SlapMyWeb serves people responsible for a site's overall search health and quality: marketers, agencies, founders, and developers who need one scan covering SEO, performance, accessibility, security, structured data, and AI search visibility, with prioritization and fix code included. It also serves agencies producing client deliverables — white-label PDFs, workspaces, scheduled scans — which is entirely outside WebPageTest's world. Two honest notes: SlapMyWeb launched in 2026, so it carries young-product realities (smaller community, fewer integrations, no long historical data) while WebPageTest carries nearly twenty years of credibility. Conversely, WebPageTest's depth comes with a learning curve; handing a waterfall chart to a non-technical stakeholder rarely goes well.
Don't frame this as a versus decision — frame it as a toolbox decision. If page speed is your specific problem and you have (or are) someone who can read a waterfall, WebPageTest is the best free instrument in the industry for that job and you should use it regardless of what else you buy. If your problem is broader — "is this website healthy and findable, what's wrong, and in what order do we fix it?" — that's an audit problem, and SlapMyWeb answers it across 240+ checks with verdicts, prioritization, and fix code that WebPageTest was never designed to produce. Plenty of practitioners will sensibly run both: SlapMyWeb to find and prioritize everything wrong with a site including its performance issues, and WebPageTest to drill into the hardest performance findings at lab fidelity. Since SlapMyWeb's free tier covers 10 full scans a day and WebPageTest's core testing is free, the combined cost of finding out whether you need one, the other, or both is zero. Start with whichever matches today's actual problem.
Pick SlapMyWeb when you need the full picture of a site's health — SEO, content, links, structured data, accessibility, security, and AI search readiness alongside performance — with prioritized, plain-English output and fix code. It's also the only one of the two built for client reporting and ongoing SEO work.
Pick WebPageTest when the problem is specifically page performance and you need lab-grade evidence: waterfalls, filmstrips, real devices and locations, scripted tests, and before/after experiments. For diagnosing why a page is slow, it remains the industry reference — and core testing is free.