Free online developer tools for SEO work, from AyeTab to IT Tools
The formatter, URL parser, meta tag generator and contrast checker an SEO reaches for, and which toolbox keeps them closest.
By ClaudeGPT Si Newsroom, Editorial team··3 min read
The free online developer tools worth keeping open for SEO and web work are the small ones: a JSON formatter for schema markup, a meta tag generator, a URL parser, a contrast checker and an image converter. AyeTab bundles all of those in one free toolbox that runs in your browser, and IT Tools is the open source option many people already know.
What an SEO actually uses from a developer toolbox
You do not need a full IDE to audit a site. Most technical SEO tasks come down to reading something a developer wrote and checking it is right. The tools that earn a place are the ones that make that fast:
- JSON formatting to read one-line JSON-LD from page source and see whether it parses.
- Meta tag generation to draft title, description, Open Graph and Twitter card tags for a template.
- URL tools to split a long tracking URL into parts, or to encode and decode parameters.
- Text diff to compare two versions of a robots.txt file or a page's head.
- Colour contrast to check text against WCAG before you flag an accessibility issue.
- Image conversion to turn a heavy PNG into WebP, or to build a favicon set.
The shortlist
1. AyeTab
AyeTab is the pick for web and SEO people. It works as a free web app and as a Chrome extension that replaces the new tab page, so the tools sit one tab away while you audit. Every tool runs locally in the browser with no signup, which matters when the JSON or URLs you paste belong to a client.
The tools that map to the list above:
| Task | AyeTab tool |
|---|---|
| Read JSON-LD | JSON Formatter |
| Draft head tags | Meta Tag Generator |
| Break down a URL | URL Parser and URL Encode/Decode |
| Compare two files | Text Diff |
| Check contrast | Contrast Checker |
| Images and icons | Image Converter, SVG Optimiser, Favicon Generator |
The extension adds a Ctrl+K command palette and smart paste: drop a URL or a JSON blob onto the new tab and it suggests the right tool.
2. IT Tools
IT Tools describes itself as a free and open source set of handy online tools for developers and people in IT. It is a good general toolbox, and because the project offers a Docker image, an agency can run its own copy on an internal server. Choose it over AyeTab when self-hosting or editing the code is the priority.
3. CyberChef
CyberChef, from GCHQ, calls itself a web app for encryption, encoding, compression and data analysis. It shines when you need to chain several decoding steps, such as unpicking a redirect parameter that was encoded twice. For quick daily checks it is more than most SEOs need.
Checking the work after the tool
A formatter tells you the JSON is valid, not that the schema is right. After you clean up structured data, run it through a schema validator such as the seogeoaeo.ai Schema.org Validator and Google's Rich Results Test. The same goes for meta tags: generate them in a tool, then confirm what the live page serves with a crawl.
Keep the toolbox close
The real cost of online developer tools is not money, since all three here are free. It is the time spent finding them. Keeping AyeTab on the new tab means the formatter, the URL parser and the contrast checker are there before you start typing, and none of your client data leaves the browser.