Free Developer & SEO Micro-Tools
22 browser-based utilities used by our own editors. Everything runs locally in your browser — no signup, no uploads, no tracking, and nothing leaves your device.
Available tools
Color Contrast Checker
Instant, private online color contrast checker that runs entirely in your browser without uploads.
Open the tool →Cron Expression Decoder
Translate cron schedules into plain English and preview the next 10 execution dates.
Open the tool →Cron Expression Generator
Create and validate cron expressions using a visual interface instead of manual syntax.
Open the tool →Fluid Typography Clamp Calculator
Generate precise CSS clamp() values for fluid text and spacing without writing multiple media queries.
Open the tool →CSV → JSON Converter
Instant CSV to JSON conversion in the browser with preview, type inference, and custom delimiters—no upload required.
Open the tool →cURL to Code Converter
Instant, private online curl converter that runs entirely in your browser without uploads.
Open the tool →Dockerfile Generator
Generate a complete Dockerfile in seconds—choose base image, commands, env vars, ports, and entrypoint, all locally in your browser.
Open the tool →Glassmorphism CSS Generator
Visually design frosted-glass UI effects and export the CSS backdrop-filter and transparency properties.
Open the tool →HTML to JSX Converter
Free html to jsx converter that runs in your browser and gives ready‑to‑use React JSX.
Open the tool →Image Base64 Converter
Instant, private online image to base64 converter that runs entirely in your browser without uploads.
Open the tool →JSON Diff Checker
Compare two JSON strings instantly, see structural and value differences side‑by‑side—entirely in your browser.
Open the tool →JSON Formatter & Validator
Pretty-print, minify and validate JSON with the exact line and column of any syntax error - fully offline, so payloads and tokens never leave your machine.
Open the tool →JSON to TypeScript Converter
Turn JSON into a ready-to-use TypeScript type or interface instantly, directly in your browser.
Open the tool →JSON↔YAML Converter
Instant, offline JSON ↔ YAML conversion in your browser – no upload, no signup.
Open the tool →JWT Decoder
Decode JWT headers and payloads instantly. Client-side processing ensures your tokens never leave your browser.
Open the tool →Markdown Table Generator
Instant, private online markdown table generator that runs entirely in your browser without uploads.
Open the tool →SERP & Meta Previewer
Preview how your page title, description, and social share images will render on Google, X, and LinkedIn, then export the HTML tags.
Open the tool →Regex Tester & Visualizer
Test and visualize regular expressions in real-time with instant match highlighting.
Open the tool →Robots & Ads.txt Validator
Catch the robots.txt rule that silently kills AdSense earnings, and generate a correctly formatted ads.txt record in the same page.
Open the tool →Schema.org JSON-LD Builder
Build valid SoftwareApplication, FAQPage or TechArticle JSON-LD from a form, with required-field validation before you copy anything.
Open the tool →SQL Formatter
Instantly format and validate SQL queries in-browser—no upload, full privacy.
Open the tool →URL Encoder / Decoder
Instant, private online url encoder decoder that runs entirely in your browser without uploads.
Open the tool →Why we built these tools
While reviewing dozens of small software products every month, we kept rebuilding the same three checks: previewing how a page looks in Google search, verifying that crawlers and AdSense can actually read a site, and generating valid structured data. Instead of keeping them private, we published them here so any developer, indie founder or blogger can use them for free.
What each tool does
- SERP & Meta Previewer — type a title and description and see the live Google snippet, the Twitter/X card, and the exact HTML meta tags to paste into your page head.
- Robots & Ads.txt Validator — paste a
robots.txtand check that Googlebot and Mediapartners-Google (the AdSense crawler) are allowed, then generate a correctly formattedads.txtrecord. - Schema.org JSON-LD Builder — produce valid
SoftwareApplication,FAQPageorTechArticlestructured data for rich results and star ratings.
Privacy
These tools are pure client-side HTML and JavaScript. The values you type stay in your browser tab and are never transmitted to our servers. You can even save the page and run it offline.
Missing a tool?
We add new utilities as our reviews require them. Tell us what you need and we will consider building it next.