Best Free Online Developer Tools to Use in 2026
A practical, opinionated list of the best free online developer tools worth using in 2026, organized by category so you can find what you need fast.
Aug 08, 2026
HTML with Tailwind classes
Examples:
Default
base
sm
640px+
md
768px+
lg
1024px+
xl
1280px+
How to Use
- Paste any HTML with Tailwind responsive classes (e.g.
sm:flex,lg:grid-cols-3). - Click Update Preview to see how it renders at each breakpoint.
- Use the example buttons to load predefined layouts.
- Enable Sync scroll to scroll all panels together.
Why Preview Breakpoints?
- See all breakpoints at once — No need to resize your browser repeatedly.
- Catch layout bugs early — Spot broken layouts across the full responsive spectrum.
- Debug responsive classes — Verify that your
sm:,md:,lg:prefixes work as intended.
Frequently Asked Questions
How does the breakpoint simulation work?
Each panel applies the corresponding Tailwind breakpoint class (sm:, md:, etc.) as a container query on the preview area. The "Default" panel shows styles without any breakpoint prefix.
Why don't the previews match my browser at actual breakpoint sizes?
Each panel wraps the content in an element with the corresponding breakpoint class. The Tailwind CSS in your project applies normally. If the panel itself is narrower than the breakpoint, the styles may not activate — this is expected behavior.
Can I preview 2xl breakpoint?
The grid shows up to xl (1280px+). The 2xl breakpoint (1536px+) is not included since most screens don't display that width comfortably in a multi-panel layout. You can resize your browser to test 2xl directly.
Last updated: 17 Aug 2026
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