Developer Tools

Format, encode, hash and generate without pasting secrets into someone else’s server.

AI API Cost CalculatorPrice your workload on every major LLM API, with prompt caching and batch discounts, from dated official prices.Base64 Encoder & DecoderEncode or decode Base64 text and files, with URL-safe and data URL support.Context Window CheckerPaste text or drop files to see which models can take it in one go, with space left for the reply.Document to MarkdownTurn Word, web pages and PDFs into clean Markdown that language models read well, without uploading anything.Hash GeneratorMD5, SHA-1, SHA-2, SHA-3 and CRC32 for text and files, plus HMAC and checksum checks.JSON FormatterBeautify, validate and minify JSON, with exact error locations and every number kept intact.LLM Token CounterExact OpenAI token counts and clearly labelled estimates for Claude, Gemini, Llama and more.llms.txt GeneratorBuild a valid llms.txt from a form or your sitemap, and check an existing one.Robots.txt GeneratorBlock AI training bots, keep AI search, and check that every rule does what you think.UUID GeneratorRandom v4 and time-ordered v7 UUIDs, in bulk, plus a UUID checker.

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Guides

How to Format JSON: Syntax Rules, Common Errors and FixesLearn the JSON syntax rules, fix the errors that break parsers (trailing commas, single quotes, comments), and know when to pretty-print or minify JSON.

Developer tools that don't see your data

Formatting JSON, decoding Base64 or hashing a file often means pasting sensitive data into a website. These tools run entirely in your browser, so API responses, tokens and files never reach a server.

Use the JSON formatter to pretty-print and validate data, the Base64 encoder and decoder for text and files, the hash generator to verify downloads, and the UUID generator for unique IDs.

Frequently asked questions

Is it safe to paste API keys or tokens?

The tools run locally in your browser and send nothing to a server. As a general habit, still rotate any secret you have pasted anywhere.

How large a JSON file can I format?

Several megabytes works well; very large files depend on your device memory.

Which hash algorithms are supported?

MD5, SHA-1, the SHA-2 family, SHA3-256 and CRC32, for both text and files.

Do I need an account?

No. Everything is free with no sign-up.