
DevTools Advanced
FullStackToolkit
DevFinanceTools
JSON Formatter & Validator
AllDevToolsHub
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DeveloperTools.Tech
120 free browser-based developer utilities. No sign-up required.

Rune codes
TinyWow
IT Tools
10015.io
SmallDevTools
Squoosh
onlinclipboard.com
Format JSON, generate passwords, convert colors, merge PDFs — 122 utilities that run entirely in your browser. No accounts, no uploads, your inputs never leave the page.

Which is more popular?
Website, pricing, platforms and company facts side by side.
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|---|---|---|
| Website | devtoolstack.io | mello.tools |
| Pricing | ||
| Platforms | — | |
| Company | — | 2026 |
| Listed in |
In their own words, as submitted to SaaSHub.


No description of DeveloperToolStack yet.
Mello is a directory of 122 utility tools that all run entirely in your browser. Format JSON, generate passwords, convert colors, merge PDFs, resize images, decode JWTs, calculate loans — every tool runs as client-side JavaScript, with no server-side processing at any step. The design rule is...
What each product offers, as listed by its team.


Possible disadvantages
An editorial look at what each product does well and who it suits.


No analysis of DeveloperToolStack yet.
Overall verdict
Why this product is good
Recommended for
How often each product is chosen within a category, 0–100% relative to the other.


As answered by people managing DeveloperToolStack and Mello.tools.
Mello.tools's answer:
Most "free online tool" sites send your input to a server you don't operate. For utilities you reach for daily — JWT decoders, image compressors, PDF mergers, password generators — that means handing potentially sensitive data to a third party you have no agreement with. Mello solves this architecturally: the site is statically generated, there are no API routes, and the only thing the server returns is HTML and JavaScript. If your input matters at all, that's the difference.
Mello.tools's answer:
Developers, designers, small-business operators, and knowledge workers — anyone who reaches for a "free online tool" several times a week. The privacy-first design especially fits people working with sensitive material (auth tokens, scanned IDs, financial data, unannounced creative assets) and people on slow or metered connections where avoiding uploads matters in practice.
Mello.tools's answer:
Mello started from a recurring annoyance: needing to do something quick — decode a JWT, compress a photo, format a JSON payload — and realizing the easiest path was to paste sensitive data into a free site I had no relationship with. The "decoded client-side" claims in small text were untestable from outside. Browser-only seemed like the obvious right answer for these kinds of utilities, so I built it that way from the start. Mello shipped in May 2026 with 122 tools across 10 categories.
Mello.tools's answer:
Next.js 15 (App Router) with full static export, React 19, TypeScript, and Tailwind CSS v4. Tool implementations use native browser APIs (Canvas, Web Crypto, FileReader, DOMParser) where possible, with carefully chosen JS libraries for the rest: pdf-lib and pdf.js for PDF handling, libheif compiled to WebAssembly for HEIC decoding, exifr for image metadata, marked and turndown for Markdown conversion, sql-formatter for SQL. Hosted on Cloudflare Pages as a fully static site.
Mello.tools's answer:
Mello is the only utility-tools directory at this scale built around a strict no-server-processing rule. Every one of its 122 tools runs as JavaScript in your browser — no uploads, no accounts, your inputs never leave the page. JWTs, photos with embedded GPS coordinates, contract PDFs, production data: none of it ever leaves your machine, because there is no server endpoint that could see it.
Share your experience with using DeveloperToolStack and Mello.tools. For example, how are they different and which one is better?
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