Over the past year, I've been building free browser-based tools at devtools-site-delta.vercel.app. What started as a JSON formatter I built for myself has turned into 500+ tools.
Most of them run entirely client-side — your data never leaves your browser. No accounts, no paywalls, no "5 free uses per day" nonsense.
Here are the 15 I use the most.
1. JSON Formatter & Validator
Paste in ugly JSON, get it pretty-printed with syntax highlighting. Also catches errors and tells you exactly where the problem is (line and character). I use this multiple times a day when debugging API responses.
2. PDF Merge
Drag in multiple PDFs, reorder them, merge into one file. Runs entirely in your browser using pdf-lib. No upload, no server. I wrote a whole post about this one.
3. Image Compressor
Drop in an image, adjust the quality slider, download a smaller version. Uses the Canvas API. I compress every image before adding it to a blog post or README. Usually saves 60-80% file size.
4. Regex Tester
Write a regex pattern, paste in test text, see matches highlighted in real time. Shows capture groups, match indices, and flags. Way faster than tab-switching to regex101 when I'm already in the zone.
5. JWT Decoder
Paste a JWT token and instantly see the decoded header and payload. Shows expiration time in a human-readable format. Essential for auth debugging. Also has a JWT creator if you need to generate test tokens.
6. QR Code Generator
Type in a URL, text, or WiFi credentials and get a QR code you can download as PNG or SVG. The WiFi QR generator is great — print one out, stick it on the fridge, and guests can connect without asking for the password.
7. Color Picker & Palette Generator
Pick a color, get the HEX, RGB, HSL, and CSS values. The palette generator creates harmonious color schemes from a seed color. There's also a contrast checker for WCAG accessibility compliance.
8. Base64 Encoder/Decoder
Encode and decode Base64 strings. Also handles image-to-base64 conversion, which is useful for embedding small images directly in CSS or HTML.
9. Hash Generator
Generate MD5, SHA-1, SHA-256, and SHA-512 hashes from any text input. Good for verifying file integrity or generating quick checksums. All computed locally using the Web Crypto API.
10. CSS Gradient Generator
Visual gradient builder with live preview. Supports linear, radial, and conic gradients. Pick your colors, adjust stops, copy the CSS. I use this instead of guessing gradient values and refreshing the browser 50 times.
11. Background Remover
Remove image backgrounds using an ML model that runs in the browser. Works great for product photos and headshots. No upload required — the model processes everything locally.
12. Markdown Preview
Split-pane editor with live rendering. I use this when writing READMEs or documentation. Also has Markdown to HTML conversion and an HTML to Markdown converter for going the other direction.
13. CSS Box Shadow Generator
Visual editor for CSS box shadows with sliders for offset, blur, spread, and color. Supports multiple shadow layers. Copy the CSS when it looks right. Saves a ton of trial-and-error.
14. JSON to TypeScript
Paste a JSON object and get TypeScript interfaces generated automatically. Handles nested objects, arrays, and optional fields. I use this constantly when working with API responses — paste the response, get the types, move on.
15. Image Resizer
Resize images to exact dimensions with aspect ratio lock. Great for making Open Graph images (1200x630), favicons, or thumbnails. Runs client-side via the Canvas API.
Honorable Mentions
A few more that didn't make the top 15 but I still reach for regularly:
Code Diff — compare two code snippets side by side
YAML to JSON — convert between YAML and JSON formats
HTML Beautify — format messy HTML
CSS Minify — minify CSS for production
Epoch Converter — convert Unix timestamps
Lorem Ipsum — placeholder text generator
UUID Generator — generate v4 UUIDs
Cron Parser — explain cron expressions in plain English
Why I Built This
I was spending way too much time on ad-covered, rate-limited tool sites. Need to format some JSON? Here's 3 pop-ups and a newsletter prompt. Need to merge two PDFs? Upload your sensitive documents to our server.
So I just started building. One tool turned into ten. Ten turned into a hundred. Now there are 500+.
Everything is free. Most tools run client-side. No accounts needed.
Bookmark devtools-site-delta.vercel.app and stop giving your data to random tool sites.
Full site: devtools-site-delta.vercel.app