Developer Tools
Developers reach for a browser tool when the alternative is spinning up a project or searching their shell history. Testing a regular expression, decoding a cron schedule someone else wrote, previewing a file without installing a viewer — these are interruptions, and the cost of context-switching to a heavyweight tool is higher than the task itself.
There are 25 developer tools here, all running client-side. You can paste real configuration, real tokens, and real files without sending them anywhere.
Regular expressions
Regex Tester matches patterns against sample input with live highlighting, which turns guesswork into something you can watch. Regex Visualizer goes further and renders the pattern as a syntax tree — the fastest way to understand an expression someone else wrote, or to find the branch that is silently matching too much.
Schedules, diagrams, and markup
Cron Expression builds schedules from fields, and Cron Expression Parser does the reverse: paste a cron string and read what it actually means in plain language. Crontab Guru explains expressions the same way, which is worth doing before trusting a schedule you inherited.
Mermaid Chart renders flowcharts from text definitions. SVG Editor edits vector markup directly with a preview. HTML Visual Editor lets you paste or upload HTML and edit it visually — a fast way to mock up a change without a build step.
Inspecting files and input
File Viewer previews 135+ formats — PDF, Word, Excel, CAD, 3D models, and images — so you can look at an attachment instead of trusting the filename. Keyboard Test confirms that key events fire, which matters for shortcuts and accessibility work.
Everything here runs in the tab, which is what makes it safe to point at production artifacts.
Frequently asked questions
Are the developer tools free?
Yes. All 25 tools are free with no account and no usage cap.
Is my code or config uploaded?
No. Processing happens in your browser; pasted content is not transmitted to a server.
Can I test production regexes safely?
Yes. Because matching runs locally, you can use real patterns and real sample data privately.
Which file formats can I preview?
File Viewer handles 135+ formats including PDF, Word, Excel, CAD, 3D, and common image types.