Most "free developer tools" lists link to GitHub repos you need Node.js to run locally, or SaaS products with a login wall. Everything below runs in a browser tab, handles your data client-side or deletes it from the server within 30 minutes, and requires no account of any kind.
All 26 tools are at at-use.com. Grouped by what you are actually trying to do.
Encoding & Decoding
Base64 Encoder/Decoder — Encode text or binary to Base64, or decode it back. UTF-8 text and binary file payloads both work. Runs in your browser — nothing sent to a server.
URL Encoder/Decoder — Percent-encode strings for safe URL inclusion, or decode percent-encoded URLs back to readable text. Handles both application/x-www-form-urlencoded and RFC 3986 encoding modes.
HTML Entity Encoder/Decoder — Convert special characters to named HTML entities (< → <, & → &) or decode entities back to characters. Useful when building template strings or sanitizing output for display.
Binary Translator — Text to binary, binary to text, or translate between binary, decimal, hex, and octal. Useful for low-level debugging and learning number representations.
Number Base Converter — Convert integers between binary (base 2), octal (base 8), decimal (base 10), and hexadecimal (base 16). All four outputs shown simultaneously.
JWT Decoder — Paste a JWT token to decode and inspect the header and payload. Runs entirely in the browser — your token never leaves your machine.
JSON & Text
JSON Formatter & Validator — Format, validate, and minify JSON in one click. Toggle between pretty-print and compact output. Syntax errors include the exact line and column number. Uses browser-native JSON.parse() — no data sent anywhere.
Text Diff — Side-by-side text comparison with no character limit (diffchecker.com caps at 25,000 characters on the free tier). JSON-aware mode auto-formats both inputs before diffing so whitespace differences do not pollute the output.
Case Converter — 12 text case formats at once: camelCase, PascalCase, snake_case, kebab-case, SCREAMING_SNAKE, Title Case, dot.case, and more. All outputs update as you type — paste once, copy whichever format you need.
Markdown to HTML — Convert Markdown to HTML with syntax highlighting for code blocks. Side-by-side preview. Clean semantic output, no inline styles.
Regex Tester — Test regular expressions against sample text with real-time match highlighting. Flags (global, case-insensitive, multiline, dotAll) can be toggled. Match groups are listed below the input.
Readability Checker — Flesch-Kincaid Grade Level, Flesch Reading Ease, Gunning Fog Index, and Automated Readability Index. Handy for checking whether your documentation or API reference copy is accessible to a broad audience.
Time & Date
Unix Timestamp Converter — Convert between Unix timestamps and human-readable dates. Handles both seconds and milliseconds. Shows UTC, your local timezone, and ISO 8601 format simultaneously.
Cron Expression Builder — Build and validate cron expressions with a visual UI. Shows the next 5 scheduled run times so you can confirm the schedule is correct before deploying.
Generators
UUID Generator — UUID v1, v4, or v7 in bulk. Set the count (1–1000), generate, copy or download as a plain text list. Browser-side only — no server involved.
Hash Generator — MD5, SHA-1, SHA-256, SHA-512 from text input or file upload. Runs in the browser using the Web Crypto API. Results copy in one click.
Password Generator — Configurable length, character sets (uppercase, lowercase, numbers, symbols), exclusion of ambiguous characters. Generate multiple passwords in one batch.
QR Code Generator — Enter any URL or text string and download a QR code as PNG or SVG. No account, no watermark.
QR Code Reader — Upload a QR code image or use your camera to scan one. Decoded entirely in the browser — nothing sent to a server.
Barcode Generator — Code 128 (alphanumeric), EAN-13 (international retail), UPC-A (US retail), and Code 39 (industrial/logistics) formats. PNG or print-ready SVG output.
Network & DNS
DNS Lookup — Query A, AAAA, CNAME, MX, TXT, NS, SOA, and PTR records for any domain.
WHOIS Lookup — Registration info, nameservers, registrar, and status for any domain.
HTTP Headers Checker — Inspect the HTTP response headers returned by any URL. Useful for debugging caching policies, CORS configuration, content-type, security headers (HSTS, CSP, X-Frame-Options), and redirect chains.
Subnet Calculator — CIDR to subnet breakdown: subnet mask, wildcard mask, broadcast address, usable host range, and binary representation. Supports IPv4 and IPv6.
Email & Deliverability
SPF Checker — Validate your SPF record, check alignment, and see a pass/fail result for a given sending domain.
DMARC Checker + DKIM Lookup + SSL Checker + BIMI Checker — The SPF tool links to all four of these, so you can step through the full email authentication audit in one go: DMARC policy, DKIM key existence, SSL certificate chain, and BIMI logo record. Five tools covering the whole stack.
The trade-off
The site is ad-supported. That is the trade: you see an ad, you get the tool, no account needed, no data stored beyond what is needed to process your file (and that is deleted within 30 minutes). Encoding and generator tools never touch a server at all.
Developer tools hub: at-use.com/tools/developer
Network/DNS tools hub: at-use.com/tools/network-dns