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About SerpPrism
SerpPrism is a small collection of SEO tools that run entirely in your browser.
Why these tools exist
Most SEO checking tools ask you to enter a URL, then crawl your site from their servers and show you a report. That is useful, but it means handing over an address you may not want logged, and waiting for a crawl you do not need if you only wanted to check one thing.
The tools here take the opposite approach: you paste the text or rules you want to check, and the analysis happens on your machine. There is no queue, no account, and no server-side record of what you checked.
What the tools deliberately do not do
They do not produce a site-wide SEO score. A single number cannot tell you which line of a robots.txt file is blocking a section, or which sentence of a paragraph is unreadable. Every tool here points at a specific thing instead, because that is what you can actually act on.
They also do not fetch live URLs. Browsers block cross-origin requests for good reasons, and a tool that worked around that would be a liability rather than a feature. If you need site-wide crawling, use a crawler — this site is for checking one thing quickly and privately.
Accuracy and limits
Where a measurement is approximate, the tool says so. The SERP preview measures rendered pixel width using the font stack and sizes Google uses on desktop results; it is accurate enough to tell you whether a snippet will be cut, and it is not a guarantee of what Google will display, because Google frequently rewrites descriptions using text from the page itself.
The robots.txt tester implements the longest-match rule from RFC 9309 including wildcards. It is not a substitute for Google's own tester in Search Console, which has access to Google's actual crawl behaviour — but it is much faster for answering "which of my rules is doing this?"
Who runs this
SerpPrism is an independent site. Questions, bug reports and corrections are welcome — use the contact page. Corrections are genuinely appreciated: if a tool here gives you a wrong answer, that is a bug worth knowing about.