▸ Free tools
Tools I built because I needed them.
Free, no-signup engineering tools that run entirely in your browser — LLM token and cost math, encoding, hashing, JSON tooling, infra sizing, Shopify helpers.
▸ 23 tools · free · no signup
▸ 100% client-side
▸ Nothing uploaded, nothing logged
AI & LLM
Budget a prompt before it bankrupts you: token math, context windows, chunking, and API spend.
- Live
LLM Cost Calculator
Estimate API spend across Claude, GPT, and friends. Tokens in/out × requests × model price — see the monthly bill before you ship.
Open
- Live
Token Counter
Paste any text and estimate token count for Claude and GPT models — plus characters, words, and a rough per-call cost. All in your browser.
Open
- Live
Context Window Checker
Will the prompt fit? Paste it and see tokens used, headroom left, and what's still free for the answer across Claude, GPT and Gemini windows.
Open
- Live
RAG Chunk Splitter
Split text into retrieval chunks — fixed, sentence, paragraph, or markdown-heading aware — and see every chunk's token count and overlap seam.
Open
Encoding & secrets
Encode, decode, hash, and generate. Every one of these runs client-side — nothing is transmitted.
- Live
JWT Decoder
Paste a JWT and read its header and payload — claims, algorithm, and expiry decoded in your browser. Decode-only; nothing is sent anywhere.
Open
- Live
Base64 Encoder / Decoder
Encode and decode base64 without the UTF-8 bugs — emoji and accents round-trip correctly. base64url and file-to-data-URI included.
Open
- Live
SHA Hash Generator
SHA-1, SHA-256, SHA-384 and SHA-512 for text or a file, in hex or base64. Web Crypto, in your browser. No MD5 — on purpose.
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- Live
Secret & API Key Generator
Keys, hex secrets and passphrases from crypto.getRandomValues — never Math.random. Unbiased sampling, entropy readout, nothing logged.
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- Live
UUID Generator
Generate v4 UUIDs in bulk, copy with one click. Crypto-random, instant, offline. Handy for seeds, fixtures, and quick IDs.
Open
Data & APIs
JSON, URLs, and schemas. The tools you reach for mid-debug with a payload in your clipboard.
- Live
URL Parser & Encoder
Break a URL into every part, edit query params and watch it rebuild. Plus the four encode/decode functions people keep mixing up.
Open
- Live
JSON Formatter & Validator
Format, minify, sort keys — and when it breaks, get the line, the column, and a caret under the exact character, not just “Unexpected token”.
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- Live
JSON to TypeScript & Zod
Paste a JSON sample, get typed interfaces plus a Zod v4 schema — unions merged, optionals inferred, dates and emails detected.
Open
Infrastructure
Cron, timestamps, permissions, bandwidth, latency, capacity. The arithmetic nobody wants to redo by hand.
- Live
Cron Explainer
Decode a cron expression into plain English, field by field. Built it for my own schedulers — paste a 5-field cron and read what it actually does.
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- Live
Epoch Converter
Unix timestamp in, human date out — UTC, local, ISO 8601, relative. Auto-detects seconds vs milliseconds, which is the bug you actually had.
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- Live
Chmod Calculator
Tick boxes or type 755 — both stay in sync. Setuid, setgid and sticky included, with the S/T rendering most calculators get wrong.
Open
- Live
Transfer Time Calculator
How long to move X at Y bandwidth. Bits vs bytes, GB vs GiB, and the protocol overhead that line-rate maths always forgets.
Open
- Live
Latency Percentile Calculator
Paste response times, get p50 through p99.9 with a histogram — and a warning when your sample is too small for the percentile you asked for.
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- Live
Server Capacity Calculator
Little's Law sizing: requests/sec × latency → workers you actually need. Includes the Erlang C queue math for what happens near full utilization.
Open
Shopify
Built while shipping Shopify apps — webhook verification and the ID formats that keep changing.
- Live
Shopify Webhook HMAC Verifier
Check a webhook signature against your client secret, constant-time, in the browser. When it fails, it tells you which of the usual causes it was.
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- Live
Shopify GID Decoder
gid://shopify/Product/123 in, resource type and legacy numeric ID out — or the reverse. Handles the base64-encoded IDs older APIs still return.
Open
Reference
Lookup tables I got tired of searching for. Status codes, headers, ports — filterable, no ads.
- Live
HTTP Status Codes
Every 1xx–5xx code with what it means and when to actually use it — including 307 vs 302, 401 vs 403, and the non-standard ones. Filterable.
Open
- Live
HTTP Headers Cheat Sheet
Request and response headers that matter in production — caching, CORS, security, forwarding — each with a real example value. Filterable.
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- Live
Common Ports
TCP and UDP ports for web, databases, caches, Docker, Kubernetes and dev servers — each with a practical note on what listens there and why.
Open