How Our Tools Work: Methodology and Data Sources
This page explains exactly how SpellMistake tools get their results: the rules they follow, the data sources they use, how we test them and what their limits are. We share this so you can trust our results and know when to double-check them.
- Every tool follows official rules and standards
- Data comes from the page you check or a named, trusted source
- We never show made-up scores or fill gaps with guesses
- Tools are tested against known answers and re-tested monthly
- We tell you the limits of every result
1. Our Principles
- Official rules first. Checks follow Google Search Central documentation and web standards, not opinions or old myths.
- Real data only. Numbers come from your page, your input or a named data source.
- Honest limits. If a source cannot answer, the tool tells you instead of guessing.
- Privacy by design. Writing tools run in your browser wherever possible.
2. The Three Ways Our Tools Work
Browser tools
Tools such as the Spell Checker, Word Counter, Article Rewriter, generators and calculators run fully in your browser. Your input stays on your device.
Page tools
Tools such as the Meta Tags Analyzer, Broken Links Checker and SEO Audit Tool ask our server to fetch the public page you enter, the same way a search engine crawler does. The server only fetches public addresses, uses time and size limits, and caches results for a few minutes.
Data tools
Tools such as the PageSpeed Checker and Domain Rating Checker send the URL or domain you enter to a trusted data provider and show its answer, with the provider named on the result.
3. How Accurate Each Tool Type Is
Accuracy depends on what a tool does. Here is an honest view of each type.
| Tool type | How it works | Accuracy | Keep in mind |
|---|---|---|---|
| Page checksMeta Tags Analyzer, Headings Extractor, Broken Links Checker, HTTP Status Checker, Redirect Chain Checker | We read the live page or server reply at the moment you run the check. | Exact | Shows what the server returned at that moment. Some sites block bots or show different pages by country. |
| Generators and validatorsRobots.txt Generator and Validator, XML Sitemap Generator and Validator, Schema Markup Generator and Validator | Built on official rules: RFC 9309 for robots.txt, the sitemaps.org protocol and schema.org. | High | Test important changes in Google Search Console before you rely on them. |
| Writing toolsSpell Checker, Grammar Checker, Article Rewriter, Word Counter | Spelling uses Hunspell dictionaries for US and UK English. Grammar uses our own rules plus LanguageTool for the deep check. | High | Names, brands and new words may be flagged. Suggestions are advice, so review them before you accept. |
| Data toolsPageSpeed Checker, Core Web Vitals Checker, Domain Rating Checker, Page Rank Checker, Domain Age Checker | Real data from trusted providers such as Google PageSpeed Insights, the Chrome UX Report and Ahrefs. | Same as source | As accurate as the source. We name the source and never fill gaps with made-up numbers. |
| Snippet previewsMeta Title Checker, Meta Description Checker, SERP Simulator | Titles and descriptions are measured in pixels to match how Google shows them. | Close estimate | Google can shorten or rewrite snippets, so use the preview as a close guide. |
| CalculatorsSEO ROI Calculator, Keyword Value Estimator, Keyword Opportunity Score, Backlink Price Calculator | Clear formulas applied to the numbers you enter. | Estimate | The maths is exact, but results depend on your inputs. Use them for planning, not as promises. |
4. Data Sources We Use
| Source | Used for |
|---|---|
| Google PageSpeed Insights API | Lighthouse speed scores and website screenshots |
| Chrome UX Report (CrUX) API | Real-user Core Web Vitals: LCP, INP and CLS |
| Ahrefs (Domain Rating API) | Domain Rating scores, shown as “Domain Rating by Ahrefs” |
| Open PageRank | PageRank style authority scores |
| Google Knowledge Graph Search API | Checking if a brand or person is a Google entity |
| YouTube Data API | Video tags and stats |
| RDAP registries | Domain age, expiry and registrar |
| Google Public DNS | DNS records, SPF and DMARC checks |
| Internet Archive Wayback Machine | Website history |
| crt.sh certificate logs | SSL certificates and subdomains |
| LanguageTool | Grammar Checker deep check |
| SCOWL Hunspell dictionaries | US and UK spelling |
| Datamuse | Related words and synonyms |
| IndexNow | Sending new URLs to Bing and other search engines |
5. Rules and Standards We Follow
- Google Search Central documentation for titles, snippets, redirects, canonicals, robots rules and structured data
- RFC 9309 for robots.txt
- The sitemaps.org protocol for XML sitemaps
- schema.org for structured data types
- web.dev Core Web Vitals thresholds for speed results
6. How We Test
Before launch, every tool runs on test cases where the correct answer is already known, and results are compared with official tools such as Google’s Rich Results Test and PageSpeed Insights. We also test edge cases and every major browser on desktop and mobile. After launch, every tool is re-tested every month, and bug reports are fixed as a high priority. See our About Us page for our full testing and review schedule.
7. Known Limits
- Some websites block automated requests, so page tools may not see them.
- Pages that change by country, device or login may look different to our server than to you.
- Data providers update on their own schedule, so numbers can differ from other tools.
- Search engines make the final ranking decisions. No tool can predict them exactly.