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ToolMill focuses on practical browser-based utilities for data cleanup, encoding, passwords, timestamps, text formatting, and everyday developer workflows.
Every tool is designed to be usable immediately, with local processing where possible so you can work with sensitive snippets, exports, and drafts more safely.
Data
JSON ↔ CSV Converter
Convert JSON to CSV or CSV to JSON instantly in your browser. Useful for spreadsheets, exports, analytics, and quick data cleanup. Supports headers, quoting, and common CSV edge cases like commas inside fields. Great for preparing imports/exports for Google Sheets, Excel, BI tools, and APIs. Runs client-side for privacy and works offline after installing ToolMill as a PWA.
Data
JSON Pretty Print, Minify, and Validate
Format JSON for readability, minify it for compact storage, and validate it before using it in APIs, config files, frontend apps, or test fixtures. This tool is useful when debugging payloads, comparing responses, cleaning copied JSON, or shrinking data for transport and logging. ToolMill processes everything in your browser, making it a fast privacy-friendly option for working with sensitive JSON.
Data
JSON to CSV Converter
Convert JSON into CSV format directly in your browser for spreadsheet imports, reporting exports, analytics workflows, and quick data cleanup. This tool is useful when you need to flatten structured JSON into rows and columns for Excel, Google Sheets, BI tools, or CSV-based systems. ToolMill runs locally for privacy, handles common export scenarios quickly, and works offline after installation.
Data
JSON ↔ YAML Converter
Convert JSON to YAML and YAML to JSON instantly in your browser. Great for config files (Kubernetes, Docker Compose, CI/CD pipelines) and for turning API payloads into readable YAML. ToolMill runs client-side for privacy, supports pretty output, and can work offline when installed as a PWA.
Data
JSON Validator
Validate JSON and get precise, line-by-line error messages. Use it to catch subtle issues like trailing commas, comments, unescaped characters, and malformed numbers before shipping configs or API payloads. Runs entirely in your browser for privacy and can work offline when installed as a PWA.
Data
YAML to JSON Converter
Convert YAML into clean, valid JSON directly in your browser for APIs, config debugging, automation workflows, and developer tooling. It is especially useful when working with Kubernetes manifests, CI/CD files, Docker Compose, and other YAML-based configuration that needs to be transformed into JSON for validation or downstream systems. ToolMill runs client-side for privacy and can work offline as a PWA.
Data
Encoding
Base64 Encode / Decode Tool
Encode text into Base64 or decode Base64 back into readable content directly in your browser. It is useful for inspecting tokens, debugging authorization headers, checking config values, decoding API payloads, and converting plain text without using a remote service. ToolMill runs fully client-side for privacy and continues to work offline after installation.
Encoding
Hex Encode / Decode — Text ↔ Hex
Hex Encode / Decode converts text into hexadecimal (base-16) bytes and decodes hex back into readable text. Use it for debugging binary payloads, inspecting UTF-8 bytes, reversing escaped strings, and working with hashes or low-level protocols. Accepts common hex formats (with or without spaces, newlines, or 0x prefixes). Runs 100% locally in your browser — no uploads — and works offline after installing ToolMill as a PWA.
Encoding
HTML Entity Encode / Decode — Escape & Unescape HTML
HTML Entity Encode / Decode converts special characters like <, >, &, and quotes into safe HTML entities (and decodes them back). Use it when working with HTML attributes, templates, CMS editors, Markdown docs, or when debugging copy/paste issues. Handles common named entities (e.g. <, >, &, ") and numeric entities. Runs 100% locally in your browser — no uploads — and works offline after installing ToolMill as a PWA.
Encoding
ROT13 Encode / Decode — Text ↔ ROT13 Cipher
ROT13 is a simple letter substitution cipher that shifts A↔N, B↔O, etc. It is often used for spoilers, light obfuscation, and forum/email text. This tool encodes plain text to ROT13 and decodes ROT13 back to text (the operation is symmetric). Runs 100% locally in your browser — no uploads — and works offline after installing ToolMill as a PWA.
Encoding
URL Encode / Decode (Percent-Encoding)
URL Encode/Decode (percent-encoding) converts unsafe characters into a URL-safe format and back again. Use it for query strings, redirect URLs, UTM parameters, and debugging API requests (RFC 3986). Runs 100% locally in your browser — no uploads — and works offline after installing ToolMill as a PWA.
Encoding
Security
Passphrase Generator — Diceware‑Style Word Passwords
Generate strong, memorable passphrases made from random words (Diceware‑style). Choose word count, capitalization, optional numbers, and a separator to create phrases suitable for logins, Wi‑Fi, and recovery codes. Uses cryptographically secure randomness when available and runs 100% locally in your browser — no uploads — with offline support as a PWA.
Security
Password Generator — Strong Random Passwords
Generate strong random passwords instantly in your browser. Choose length and optional character sets (uppercase, lowercase, numbers, symbols) to create secure passwords for accounts, Wi‑Fi, API keys, and apps. Uses cryptographically secure randomness when available. Runs 100% locally — nothing you type is sent to a server — and works offline after installing ToolMill as a PWA.
Security
Random String Generator
Generate random strings instantly in your browser for test data, invite codes, temporary IDs, mock API keys, filenames, and developer workflows. Choose the length and character sets you want—such as lowercase letters, uppercase letters, numbers, or symbols—to create output that fits your use case. ToolMill runs fully client-side, so nothing you generate is uploaded to a server.
Security
SHA-256 Hash Generator
Generate SHA-256 hashes in your browser for checksums, content verification, reproducible fingerprints, API testing, and debugging across systems. It is useful when comparing values, validating downloads, or confirming that text inputs produce the expected digest. ToolMill performs hashing locally for privacy; for password storage, use a dedicated password hashing algorithm such as Argon2, bcrypt, or scrypt instead of plain SHA-256.
Security
UUID v4 Generator
Generate UUID v4 values instantly in your browser for database records, API requests, correlation IDs, log tracing, fixtures, and distributed systems. This tool is useful when you need quick unique identifiers during development, testing, or manual data entry without relying on a CLI or external service. ToolMill keeps generation local and does not send your data anywhere.
Security
Text
Remove Duplicate Lines
Remove duplicate lines while keeping the first occurrence of each value. Useful for cleaning email lists, log output, keyword exports, CSV snippets, copied spreadsheet columns, and prompt inputs before you paste them elsewhere. ToolMill runs entirely in your browser, so sensitive text never has to leave your device.
Text
HTML to Plain Text Converter
Convert HTML to plain text when cleaning email templates, scraped snippets, CMS exports, support content, or copied web pages. It helps you remove markup quickly while preserving readable text for notes, documents, prompts, or downstream processing. ToolMill does the conversion in-browser, which is useful when the source HTML contains private or client-sensitive content.
Text
Markdown to HTML Converter
Convert Markdown to HTML when preparing blog posts, documentation, README content, CMS entries, emails, or knowledge-base articles. It is helpful for checking how headings, emphasis, lists, and code-style content will render before publishing. ToolMill runs locally in your browser, making it a quick privacy-friendly alternative to online converters that upload your draft text.
Text
Remove Empty Lines from Text
Remove blank lines from pasted text instantly while keeping the remaining lines in the same order. This is useful for cleaning logs, lists, copied spreadsheet columns, CSV or TSV snippets, code blocks, email drafts, and text pulled from PDFs or chat exports. ToolMill runs entirely in your browser, so private text stays on your device.
Text
Slugify Text for SEO-Friendly URLs
Turn titles, headings, product names, and article ideas into clean URL slugs for blogs, CMS entries, landing pages, and developer routes. It is useful when you want readable, SEO-friendly URLs without punctuation or spacing issues. ToolMill gives you a fast in-browser result without ads, account walls, or sending draft page titles off-site.
Text
Alphabetize and Sort Lines
Sort lines alphabetically to organize pasted lists, keyword sets, product SKUs, hostnames, file names, and checklist items. It is handy for quick cleanup before deduping, diffing, or importing data into another system. ToolMill keeps the work client-side for speed, privacy, and no-login convenience.
Text
Text Case Converter
Convert text case instantly — UPPERCASE, lowercase, Title Case, and Sentence case. Ideal for headlines, blog titles, email subject lines, product listings, UI labels, and general writing cleanup. Fix inconsistent capitalization, normalize ALL CAPS, and format text for documents, spreadsheets, and presentations. Runs client-side in your browser for speed and privacy (your text is not sent to a server).
Text
Whitespace Trimmer
Normalize messy whitespace in text by collapsing repeated spaces, tabs, or mixed space+tab runs into a single space. Useful for cleaning copied text from PDFs, emails, spreadsheets, and logs; formatting JSON/CSV headers; and fixing alignment issues caused by inconsistent tab/space usage. Choose whether to compress spaces, tabs, or both—output is generated separately so you can compare before/after safely.
Text
Word, Character, Line, and Byte Counter
Count words, characters, characters without spaces, lines, and UTF-8 bytes for essays, blog posts, ad copy, product descriptions, SMS drafts, API payloads, and social posts. This is useful when you need to stay under publishing limits or compare text lengths quickly. ToolMill works instantly in your browser, so you can analyze drafts without sending them to a third-party server.
Text
Development
Unix Timestamp and Epoch Converter
Convert Unix timestamps and epoch seconds into readable dates, or turn human time back into epoch values for logs, APIs, databases, analytics events, and debugging. It is especially useful when working across backend systems, JavaScript dates, and monitoring tools. ToolMill performs the conversion instantly in your browser so you can inspect time values without exposing internal timestamps to another service.
Development
ISO 8601 Timestamp Validator and Formatter
Validate ISO 8601 timestamps and normalize formatting for APIs, JSON payloads, audit logs, schedules, feeds, and database exports. Use it to catch malformed dates before they break integrations or create timezone confusion. ToolMill runs fully client-side, which makes it convenient for checking production-like values without sending them to another validator service.
Development
URL Query String Parser and Builder
Parse URL query strings into readable key/value data and rebuild them when testing links, tracking parameters, filters, redirects, signed URLs, or app state in the browser. It is useful for debugging marketing URLs, API requests, and web-app routing behavior. ToolMill gives you a quick private workspace in the browser instead of making you paste real customer URLs into a remote tool.
Development
Financial
Credit Card Number Validator Tool
Validate a credit or debit card number locally using the Luhn check digit and common issuer prefix and length rules. This tool can help catch typos and identify likely card brands such as Visa, Mastercard, American Express, and Discover, but it does not contact any bank, charge anything, or confirm that a card is active or usable.
Financial
Residential Mortgage Amortization Schedule Calculator
Calculate a residential mortgage payment and full amortization schedule locally in your browser. Compare loan amounts, rates, terms, taxes, insurance, and extra principal payments without sending financial details anywhere.
Financial
Commercial Mortgage Amortization Schedule Calculator
Calculate a commercial mortgage payment and amortization schedule locally in your browser, including balloon terms and amortization periods. Model principal, rate, term, amortization, and extra payments without sharing financial data.
Financial