A curated set of browser-based utilities for everyday text processing — word counting, JSON formatting, diffing, case conversion, Base64, URL encoding, and hashing. No signup, no server uploads, no limits.
Updated August 2026 · 4 minute read
Most free online tools work by sending your data to a server, processing it there, and sending it back. That's a problem when the data is sensitive — API keys, config files, private strings. The seven tools below share one design principle: everything runs in your browser. Nothing leaves your machine.
Each tool is self-contained HTML with inline JavaScript. You can even save the page and use it offline once loaded.
Count words, characters, sentences, paragraphs, and syllables. Get estimated reading time and a Flesch readability score. The essential content-writing utility — useful for blog posts, copy, and documentation.
Beautify, minify, and validate JSON with precise line/column error messages. Catches syntax errors before they reach your API. Supports both pretty-print and compact modes with configurable indentation.
Compare two texts side-by-side. Every added and removed line is highlighted, with options to ignore case or whitespace. Essential for code reviews, config comparisons, and spotting changes in copied text.
Convert text between eight case styles instantly: UPPERCASE, lowercase, Title Case, Sentence case, camelCase, PascalCase, snake_case and kebab-case. Also shows word and character counts. Great for normalising variable names and headings.
Encode text to Base64 or decode it back with full UTF-8 support — emoji, æøå and CJK characters round-trip exactly. Clear error messages on invalid input. Useful for data URIs, API tokens, and quick inspection of encoded payloads.
Encode special characters for safe URL transmission or decode percent-encoded strings back to readable text. Supports both full (encodeURIComponent — encodes &, +, /, =) and partial (encodeURI — preserves URL structure) modes. Handles UTF-8 characters like æøå and emoji correctly.
Compute SHA-256, SHA-512, SHA-384 and SHA-1 digests of any text using the browser's own Web Crypto API — the same implementation the browser uses for TLS. Output is lowercase hexadecimal, with per-algorithm copy buttons. Useful for checksum verification, cache-busting identifiers, and integrity checks.
| Tool | Best for | API used |
|---|---|---|
| Word Counter | Blog posts, copy, reading time | TextEncoder + regex |
| JSON Formatter | API payloads, config files | JSON.parse + custom formatter |
| Text Diff Checker | Code review, config comparison | diff.js (client-side LCS) |
| Case Converter | Variable names, headings, slugs | regex replace, .toUpperCase() |
| Base64 Encoder/Decoder | Data URIs, API tokens | btoa/atob + UTF-8 conversion |
| URL Encoder/Decoder | Query parameters, API calls | encodeURIComponent / decodeURIComponent |
| Hash Generator | Checksums, integrity fields | Web Crypt API (crypto.subtle.digest) |
Every tool is a single HTML file with inline JavaScript. There is no backend API call for processing — your text stays in your browser tab.
No network latency means results appear as you type (debounced at 250ms). Even large documents process in under a second.
No accounts, no rate limits, no watermarks, no daily caps. Each tool is self-contained and works offline once loaded.
Browse all tools from one page:
View all free tools →Related: HTML to Markdown from the terminal — One of the tools developers reach for most: convert HTML to Markdown straight from the CLI.