Mello.tools
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.
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.
This page is designed to help you find out whether Mello.tools is good and if it is the right choice for you.
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 simple: no uploads, no accounts, your inputs never leave the page. That makes Mello safe for the everyday moments where you'd otherwise paste sensitive data into a free online tool — a JWT containing a real session, a scanned passport, a photo with embedded GPS coordinates, a production database export. The catalog spans developer utilities, finance calculators, image and PDF tools, design generators, text utilities, password generation, hashing, and more. Free, no signup, no paid tier.
Listed in
Tool count
122 utilities across 10 categories
Browser-only architecture
Every tool runs as client-side JavaScript; no server processing at any step
Privacy by design
No uploads, no accounts; your inputs never leave the page
Free with no paid tier
No usage limits, no premium features, no signup required
Developer tools
JSON/XML/HTML/CSS/JS/SQL formatters, regex tester, JWT decoder, Base64/URL encoders, hash generator, UUID, cron parser, subnet calculator
Image tools
Compression, resize, crop, format conversion (PNG/JPG/WebP/HEIC/AVIF), EXIF viewer, SVG optimizer, color picker
PDF tools
Merge, split, rotate, image-to-PDF, PDF-to-image (JPG/PNG/WebP)
Design tools
Color converter, palette generator, WCAG contrast checker, CSS box-shadow / border-radius / cubic-bezier / glassmorphism / gradient generators, favicon generator
Finance calculators
Loan amortization, mortgage, ROI, compound interest, profit margin, break-even, VAT/sales tax, invoice PDF generator
Text utilities
Case converter, word counter, text diff, line tools, slug generator, Lorem Ipsum, Morse translator, fancy text
Security tools
Cryptographically random password generator (Web Crypto API), passphrase mode, password strength checker, MD5/SHA-1/SHA-256/SHA-512 hashing
Date & time tools
Date math, Unix timestamp converter, age calculator, countdown, time zone converter, stopwatch, Pomodoro focus timer
Image format guides
13 long-form articles on PNG vs JPG, WebP vs AVIF, HEIC conversion, social media image sizes
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.
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 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.
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 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.
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Check the traffic stats of Mello.tools on SimilarWeb. The key metrics to look for are: monthly visits, average visit duration, pages per visit, and traffic by country. Moreoever, check the traffic sources. For example "Direct" traffic is a good sign.
Check the "Domain Rating" of Mello.tools on Ahrefs. The domain rating is a measure of the strength of a website's backlink profile on a scale from 0 to 100. It shows the strength of Mello.tools's backlink profile compared to the other websites. In most cases a domain rating of 60+ is considered good and 70+ is considered very good.
Check the "Domain Authority" of Mello.tools on MOZ. A website's domain authority (DA) is a search engine ranking score that predicts how well a website will rank on search engine result pages (SERPs). It is based on a 100-point logarithmic scale, with higher scores corresponding to a greater likelihood of ranking. This is another useful metric to check if a website is good.
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