Free · nothing leaves your browser

Tools

Grouped by what you were doing when you came looking, not by what the tool technically is. Everything runs client-side — there is no server to send your input to.

Open every day7 Get it into another shape7 When prod misbehaves4 Wiring up an LLM5 Secrets and crypto4 Config and cloud5 Shipping a page5 Money questions3 Running the work1 Words that ship2

Openevery day

The handful that get used until they're muscle memory. If you only bookmark one row on this page, it's in here.

JSON Formatter & Validator Format, validate and repair JSON without losing a digit: big numbers stay exact. Tree and table views, JSONPath queries, a structural diff and JSON Schema generation. Diff Compare two texts line by line, or compare two prompts with estimated token counts and a word-level diff. Nothing is run against a model — all client-side. Regex Tester (JavaScript) Test JavaScript (ECMAScript) regular expressions with real-time match highlighting and group capture display. Other flavours (PCRE, Python, Go) differ. All client-side. JWT Decoder Paste a JSON Web Token and instantly decode the header, payload, and signature — all client-side. Encode & Decode Base64 and URL encoding both ways, and images to Base64 data URIs — all client-side, nothing uploaded. UUID Generator Generate cryptographically random v4 UUIDs in bulk — all client-side. Unix Timestamp Converter Convert between Unix timestamps and human-readable dates — all client-side.

Get it intoanother shape

Data goes in one format and comes out another. Unglamorous, constant, and the reason most people open a tools site at all.

Data Converter Convert YAML ⇄ JSON, CSV → JSON and JSON → CSV, with type inference for CSV — all client-side. The YAML parser is basic (no anchors, merge keys or multiple documents). SQL Formatter Pretty-print and format SQL queries with keyword highlighting. Generic SQL: no dialect-specific handling — all client-side. Markdown Convert Markdown to HTML with a live preview, and build Markdown tables in a grid — all client-side. .env File Formatter Sort, dedupe, lint, and clean your .env files. Catch unquoted values, duplicate keys, and exposed secrets. Units & Number Bases Convert units of length, weight, temperature, data size, time and more, and numbers between binary, octal, decimal and hex. Timezone Converter Compare times across multiple timezones at a glance — with business hours highlighting and common region presets. Square Texter Type a word, see it rendered as a corner-square pattern. Instant, in-browser.

When prodmisbehaves

Headers, DNS, certificates, CORS. The questions you ask at the point where something works locally and not in production.

HTTP Headers & CORS Paste HTTP response headers for security recommendations and a rule-of-thumb grade, or paste CORS headers and analyse them against the origin, method and headers you expect. Nothing is fetched. HTTP Status Code Reference Searchable reference for every HTTP status code with descriptions, use cases, and quick copy. DNS Lookup Query A, AAAA, MX, TXT, CNAME and NS records through Cloudflare's DNS-over-HTTPS service, with TTL values and copy-friendly output. The domain you type is sent to Cloudflare, not resolved by your own resolver. AWS Region Latency Tester Rough browser-to-region round-trip times for the AWS regions listed here (as of October 2026). Includes connection setup, so treat the numbers as indicative.

Wiring upan LLM

Context budgets, chunking, retrieval and prompts. The part of the work that is mostly arithmetic and mostly ignored until the bill arrives.

Token Counter Estimate token counts for GPT-4, GPT-3.5, and Claude 3 models. See character count, word count, and per-model token estimates in real time. Model Context Window Comparison Visual bar chart comparing context window sizes across GPT, Claude, Gemini, Llama, Mistral, and Cohere models. See what fits in each window. AI Cost Calculator Estimate and compare API costs across GPT-4o, Claude 3.5 Sonnet, Gemini 1.5 Pro, and more. Calculate per-request, daily, monthly, and yearly spend. RAG Chunking & Keyword Scoring See how text splits into chunks (sizes in characters), then rank chunks against a query with lexical BM25 and TF-IDF scoring. Keyword scoring only, not embeddings, so it cannot diagnose a dense-retrieval pipeline. Prompt Template Builder Write prompt templates with {{variable}} placeholders, fill in each variable, and preview the rendered prompt ready to copy.

Secretsand crypto

Hashes, keys, one-time codes and policies. All of it runs locally — nothing you paste here leaves the tab.

Hashes & SRI Hash text with MD5, SHA-256 and SHA-512, and generate Subresource Integrity hashes for scripts and stylesheets — all client-side. Passwords Generate strong random passwords with live entropy, and check how long a password would take to crack. TOTP Code Generator Generate time-based one-time passwords from a secret key — runs entirely in your browser. CSP Header Builder Build Content-Security-Policy headers interactively with directive explanations and live preview.

Configand cloud

The files and expressions you write once a quarter and have to look up every single time.

Cron Expression Builder Build, parse, and preview cron expressions with visual selectors, human-readable descriptions, and next-run previews. Nginx Config Generator Generate a starting-point nginx server block with SSL, reverse proxy, PHP-FPM and security headers. Review it before use: no rate limiting, a short cipher list. Subnet Calculator Parse CIDR notation and instantly see network address, broadcast, netmask, usable host range, and IP class. robots.txt & Sitemap Build a robots.txt with per-crawler rules and an AI-crawler preset (list as of October 2026), and an XML sitemap. Google ignores sitemap priority and changefreq. Changelog Generator Paste conventional commits and generate a formatted changelog grouped by type.

Shippinga page

Layout, colour, type, and the metadata that decides what your link looks like when somebody pastes it into Slack.

Colour & Contrast Check WCAG contrast for text on a background, and convert colours between HEX, RGB and HSL — all client-side. CSS Playground Build gradients, box shadows, flexbox and grid layouts visually, and copy the CSS — all client-side. Meta Tags & Social Preview Generate SEO, Open Graph and Twitter Card meta tags, and see a rough mock-up of link cards from the fields you enter. Nothing is fetched from your URL. Favicon Generator Upload an image and get PNG favicon and app-icon sizes plus the HTML snippet — all client-side. It does not make a .ico, an SVG favicon or a site.webmanifest. QR Code Generator Generate QR codes from any text or URL — download as PNG, all client-side.

Moneyquestions

SaaS metrics and the back-of-envelope maths behind pricing, runway, and whether a piece of work is worth doing at all.

SaaS Metrics Unit economics, MRR and ARR, churn, LTV:CAC, conversion funnel, break-even and runway — the SaaS arithmetic in one place. Freelance Rate & Scope Turn a target salary into an hourly rate with overhead and margin, and estimate a project's hours and cost with t-shirt sizes. Invoice Generator Fill in your business details, add line items, and print or save the invoice as a PDF from your browser's print dialog — no account needed, all client-side.

Runningthe work

Planning, prioritising, and the ceremonies. Lightweight versions of things that usually arrive as a $12-per-seat subscription.

Prioritisation & Decisions Rank features with ICE or RICE scoring, or weigh options against criteria in a decision matrix.

Wordsthat ship

Headlines, readability, and the copy checks worth running before a page goes out.

Headlines & Subject Lines Rule-of-thumb checks for headlines and email subject lines: length, word balance, power words, urgency and spam words. A word-list heuristic, not measured engagement. Word Count & Readability Count words, characters and sentences with reading time, and score readability with Flesch, Gunning Fog and more.