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JustDevTools
  • JSON formatter and validator
    Format, minify and validate JSON, with the exact line and column of any syntax error.
  • JWT decoder
    Read a JWT's header and payload, with issued-at and expiry times shown as real dates.
  • Base64 encoder and decoder
    Encode and decode Base64 and Base64URL, with full Unicode support.
  • JSON to TypeScript, Zod and Java
    Paste a JSON response and get TypeScript interfaces, a Zod schema or Java classes with Jackson annotations.
  • YAML to JSON converter
    Convert YAML to JSON and JSON to YAML, with the exact line of any syntax error. Handles multi-document files.
  • Regex tester
    Test JavaScript regular expressions with live match highlighting, capture groups and replace preview.
  • URL encoder and decoder
    Percent-encode and decode URLs and query values, and break a URL into its parts and parameters.
  • Unix timestamp converter
    Convert Unix timestamps in seconds or milliseconds to dates, and dates back to timestamps.
  • Cron expression explainer
    See what a cron expression means in plain English, what each field does and the next times it will run.
  • JSON to CSV converter
    Turn a JSON array into CSV for Excel or Google Sheets, or a CSV file into JSON. Nested objects become columns.
  • UUID generator and inspector
    Generate UUID v4 and time-ordered v7 in bulk, or paste a UUID to see its version and timestamp.
  • Text diff checker
    Compare two texts line by line and see exactly what was added, removed or changed.
  • Hash and HMAC generator
    SHA-256, SHA-1, SHA-384 and SHA-512 hashes and HMAC signatures of text, in hex or Base64.
  • Markdown previewer
    Write Markdown on the left and see it rendered live on the right, with GitHub-style tables and task lists.

Text diff checker

Compare two texts line by line and see exactly what was added, removed or changed.

Runs locally. Nothing you paste leaves this tab.

Differences

+3 −2
11 server:
2− port: 8080
2+ port: 8443
33 timeout: 30s
4+ tls: true
45 logging:
5− level: info
6+ level: debug

Comparing two texts

Paste the original on the left and the new version on the right. Added lines are marked + and removed lines −, with line numbers from both sides. A changed line shows as a removal followed by an addition. The comparison uses the Myers algorithm, the same one git diff uses by default, so it finds the smallest set of changes.

Options

  • Ignore whitespace treats lines as equal when they differ only in indentation, trailing spaces or repeated spaces. Use it after a reformat, or when tabs and spaces are mixed.
  • Ignore case treats SELECT and select as the same.
  • Only changed lines and context hides unchanged stretches and keeps 3 lines either side of each change, like a code review.

Comparing JSON

JSON from two systems often has the same data with different key order or formatting, and a line diff then shows everything as changed. Run both through the JSON formatter with “Sort keys” on first, then compare the results here.

Copy as patch

“Copy as patch” gives you a unified diff, the format git diff and code review tools use. Paste it into a ticket or chat to show exactly what changed.

From the command line

diff -u original.txt changed.txt
git diff --no-index original.txt changed.txt   # works outside a repo
git diff --word-diff                            # changes within lines