Free Developer Tools in 2026: The 60-Tool Stack

By Λ · May 18, 2026 · 15 min read

I have been collecting and building free online developer tools for over a year. The collection grew because every time I needed a tool, the existing options were either slow, ad-heavy, or quietly uploading my data to a server I had never heard of. So I built my own. This post is the result: a guided tour of the 60+ tools I actually use, what each is for, when to reach for it, and what to avoid.

The tools are organized by category. Each entry includes a short description, a link to the tool, and (where relevant) a note about what makes the right tool for the job. Everything here runs entirely in your browser. Nothing uploads your data. The whole list is one page so you can ctrl-F to find what you need.

Code formatting and conversion

Formatters live or die on accuracy. A "JSON beautifier" that silently mangles your unicode escapes is worse than no tool at all. The ones I trust:

JSON Formatter: beautify, minify, validate. The most-used tool on the site. Pairs with the JSON guide.
SQL Formatter: handles MySQL, Postgres, BigQuery, Snowflake dialects.
HTML Beautifier: indents minified HTML so you can read it.
JS Minifier and CSS Minifier: shrink output for production.
GraphQL Formatter: queries embedded in code get squashed; this puts them back.
Code Diff: side-by-side compare two text blobs. Faster than launching a desktop diff tool.
HTML to JSX: converts HTML attributes to JSX-style (className, etc.).
HTML ↔ Markdown: round-trip converter, useful for content migrations.

What I do not use

"Code prettifiers" that require pasting into a textarea on a site with five popups. Open Prettier in your IDE, or use my tools, or use prettier --stdin from the CLI. Browser-based formatters with intrusive ads are not worth the friction.

Data formats: JSON, YAML, CSV, XML

Almost every developer day involves moving data between formats. The conversions are simple in principle but full of edge cases (Norway problem in YAML, trailing commas, type coercion). The right tool handles the edge cases without warning.

JSON ↔ YAML: bidirectional, preserves comments where YAML supports them.
TOML Converter: rust's favorite format, gaining ground in Python (pyproject.toml). Hands-down the cleanest config format for flat data.
JSON ↔ CSV: needed monthly for analytics dumps.
JSON ↔ XML: rare but useful when integrating with legacy systems.
JSONPath Tester: live evaluation against any JSON.
JSON Schema: validate a JSON document against a schema.
JSON to TypeScript: generate type definitions from sample JSON. Huge time-saver for API integration.
XML Formatter: still relevant for SOAP, RSS, configuration files.

For deeper comparison of when to use which format, see YAML, TOML, JSON5: when each format wins.

API and HTTP tooling

API Tester: fire HTTP requests from the browser with custom headers. Postman alternative for quick checks.
Curl to Code: converts curl commands to Python, JS fetch, Go, Node http, more.
HTTP Status Codes: lookup tool. Why was that 422? What is a 451? Pair with HTTP methods reference.
User Agent Parser: figure out what browser made a request.
MIME Types Lookup: which Content-Type for that file extension?

For the deep CORS debugging flow, see the CORS post. For API testing patterns, see API testing without Postman.

Encoding and decoding

Base64: the most used encoder. Embed binary in JSON, decode email attachments.
URL Encoder: handle %20 and friends.
HTML Entities: convert & to & and back.
Binary ↔ Text: occasionally needed for low-level work.
Hex Editor: view file bytes in hex.
Unicode Converter: char to code-point and back. Handle weird quotes.
Morse Code: niche, but it exists.
Caesar Cipher: trivial cipher for CTF puzzles. Never use for real security.
Number Base Converter: bin/oct/dec/hex. Useful for bit manipulation.
Image to Base64: embed images directly in CSS or HTML.
Gzip: compress text, see compression ratio.

For the conceptual deep-dive, see understanding character encoding.

Security, hashing, and auth

Hash Generator: MD5, SHA-1, SHA-256, SHA-384, SHA-512. For file integrity, NOT for passwords.
Bcrypt Generator: real password hashing. Configurable cost.
HMAC Generator: keyed hashes for webhook signatures, JWT signing, API request signing.
JWT Decoder and JWT Generator: read and mint signed tokens.
TOTP / 2FA Generator: build authenticator-compatible secrets. Pair with the TOTP explainer post.
Basic Auth Header: build and decode Authorization: Basic headers.
SSH Keygen: generate SSH key pairs in the browser.
SSL Decoder: parse certificates to see subject, expiry, SAN.
Password Generator: cryptographically random passwords with configurable rules.
UUID Generator and UUID + NanoID Generator: v1/v4/v6/v7 plus NanoIDs.

The full 2026 password-hashing recommendation is in this post. UUID v7 migration is covered here.

Image processing

Image tools are the category where "client-side" really matters. Uploading personal photos to a random tool is a privacy hazard most users do not think about.

Image Compressor: PNG, JPEG, WebP with configurable quality.
Image Resizer: width/height with aspect-ratio lock.
Image Converter: PNG/JPEG/WebP/HEIC/AVIF cross-conversion.
Image Upscaler: 2x/4x upscaling via ONNX model in WebAssembly.
Background Remover: client-side foreground extraction.
EXIF Viewer: see and strip embedded metadata. Critical before publishing personal photos.
SVG Converter: rasterize SVG to PNG at any size.
QR Code Generator: URLs, text, WiFi, contact cards.
Aspect Ratio Calculator: trivial but used constantly.
Favicon Generator: produce favicons in all the sizes browsers expect.
Code Screenshot: render code blocks as styled images for social posts.
ASCII Art: convert image to ASCII for retro effect.
OCR: extract text from images via Tesseract WASM.
OG Preview: see how a URL renders in Twitter/Facebook share cards.

Background on why I built these client-side: browser canvas is faster than you think. Image-metadata privacy: protecting your privacy from EXIF.

CSS, color, and design

Color Picker: hex/RGB/HSL/OKLCH cross-conversion.
Color Palette: generate harmonic palettes from a base color.
WCAG Contrast Checker: pass/fail against AA and AAA.
Color Blindness Simulator: see your designs as users with CVD do.
CSS Gradient Generator: visual editor for linear and radial gradients.
Box Shadow Editor: live editor for box-shadow with multi-shadow support.
CSS Clip-Path Generator: 25 visual preset shapes.
CSS Layout Generator: flexbox and grid recipes with copy-paste output.
Cubic Bezier Editor: visual easing-curve editor.

Deep dives: modern CSS layouts, CSS color in 2026, color accessibility for developers, designing for color vision deficiency.

Date, time, and scheduling

Timestamp Converter: Unix epoch ↔ human-readable.
Date Difference Calculator: between two dates, with working-days option.
Timezone Converter: IANA-based with DST handling.
Cron Parser: human-readable description.
Cron Visualizer: see the next 10 runs.

Network, DNS, and IP

DNS Lookup: A/AAAA/MX/TXT/NS/CAA/DS via Cloudflare DoH.
IPv4 Subnet Calculator: CIDR math, usable hosts, broadcast address.
chmod Calculator: Unix permissions to octal and back.

Pair with: DNS records reference, subnet math post.

Text and content

Text Tools: sort, dedupe, reverse, shuffle, count.
Text Diff: line-by-line comparison.
Case Converter: camelCase, snake_case, PascalCase, kebab-case.
Word Counter: counts plus reading time estimate.
Slug Generator: URL-safe identifiers with diacritic handling.
Markdown Editor: live preview side-by-side.
Markdown Table: visual table editor that outputs MD.
Markdown TOC: auto-generated from headings.
Lorem Ipsum: configurable placeholder text.
Regex Tester: live evaluation with match groups.

Generators and SEO

Meta Tag Generator: build SEO and Open Graph meta tags.
Robots.txt Generator: control crawler access.
Schema to Code: generate types from JSON Schema.

AI / LLM tools

LLM Token Counter: estimate tokens and cost across GPT, Claude, Gemini, Llama. Pair with the cost-control post.

This category is small because I am picky. Most "AI tools" online are wrappers around a single LLM API call, which makes them either an unauthorized free OpenAI endpoint or a way to harvest user prompts. Token counting is the one AI-adjacent tool that genuinely belongs entirely in your browser.

Gaming randomizers

Off-topic for serious developer work but useful for the games I actually play with friends. Eleven tools covering Fortnite, Warzone, PUBG, CS2 (weapons + strat roulette), Marvel Rivals, Dota 2, LoL, R6, Valorant, Apex Legends, Overwatch, Deep Rock Galactic, Helldivers 2, Elden Ring. Rosters are hand-maintained; see how I keep them current.

Reference content

Cheat sheets and reference pages I find myself coming back to:

HTTP Methods Reference: GET/POST/PUT/PATCH/DELETE semantics
DNS Records Reference: A, AAAA, CNAME, MX, TXT, all of them
ASCII Table: every control char and printable
Developer Glossary: definitions for the terms across this list

What I deliberately do not have

To save you searching, here is what BoltQuickTools does NOT do, with rationale:

WHOIS lookup: requires server-side because the WHOIS protocol is not browser-accessible.
Port scanner: cannot run client-side; running one server-side has legal complications.
Webhook tester: needs a server to receive the webhooks. Use webhook.site or similar.
Email tester: same reason as webhook.
Crypto trading tools, ROI calculators, gambling odds: AdSense-restricted niches; out of scope.
Anything that requires uploading a file to a third-party server for processing: violates the architecture.

How I evaluate a new tool to add

Four questions:

Can it run entirely client-side? If not, skip.
Is the existing landscape good? If three popular tools already do this well, I do not need to add a fourth.
Do I personally use this tool? If not, I cannot maintain it well.
Is there a privacy reason to keep it local? Bonus points; these are the tools where BoltQuickTools is most clearly better than the alternatives.

Closing

The full catalog updates regularly. Bookmark the homepage for the searchable grid. The blog covers the deep technical reasoning behind specific tools and patterns. If you spot a gap in this list that fits the criteria above, email me.