KATR Web Tools
22 self-contained web tools. Everything runs in your browser.
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Data & Encoding Validate, convert, hash and encode data.
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JSON Validator & Pretty Print
Validate a JSON payload and produce a pretty-printed version. Shows precise diagnostics for any errors.
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J↔
JSON Converter & Query
Convert JSON to YAML or CSV (and back), and run JSONPath queries against a document.
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B64
Base64 Encoder / Decoder
Encode text to Base64 or decode Base64 back to text, tolerant of line-wrapped and URL-safe input.
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%
URL Encoder / Decoder
Percent-encode text for use in a URL, or decode a percent-encoded string back to plain text.
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#
Hash & HMAC Generator
Compute MD5, SHA-1, SHA-256, SHA-384 and SHA-512 digests of text or a file, with optional HMAC.
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JWT
JWT Decoder
Decode the header, payload, and signature segments of a JSON Web Token.
Text & Docs Compare, clean up and render text.
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±
Text Diff Checker
Compare two blocks of text side by side or inline, with line and word-level highlighting.
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Aa
Text Utilities
Word and character counter, case converter, sort and de-duplicate lines, and find and replace.
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.*
Regex Tester & Builder
Test regular expressions against multi-line data. Choose from common patterns or build your own.
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MD
Markdown Viewer
Drag and drop Markdown files to render them, including Mermaid diagrams and links between documents.
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Li
Lorem Ipsum Generator
Generate placeholder Lorem Ipsum text by paragraphs, sentences, or words.
Generators Create passwords, IDs and QR codes.
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***
Password Generator
Generate strong, customizable passwords with a live strength estimate.
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ID
UUID & ULID Generator
Generate UUID v4, UUID v7 and ULID identifiers in bulk, with formatting options and copy.
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QR
QR Code Generator
Create styled QR codes with custom patterns, eyes, colors, frames, and an embedded logo. Download as PNG or SVG.
Color & Design Colors, CSS helpers and images.
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Color Tools
Pick and convert colors, browse web-safe and named colors, check contrast, build palettes and gradients.
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CSS Generators
Visual builders for box-shadow, border-radius and flexbox layouts that output copy-ready CSS.
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Img
Image Tools
Resize, compress and convert images in your browser, or turn an image into a Base64 data URI.
Time & Dates Timestamps, schedules and calendars.
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Ts
Timestamp Converter
Convert Unix epoch seconds or milliseconds to readable dates in any timezone, and back.
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⏱
Cron Expression Explainer
Translate a cron expression into plain English and preview its next run times.
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31
Annual Calendar
Browse a full-year calendar with all 12 months. Navigate years with the arrow buttons.
Converters & Reference Unit conversions and cheat sheets.
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