Free Tools

Online Developer Tools: JSON, Regex, JWT, Unix Timestamp and CSV

Choose a tab below. Each tool also has its own page if you want a direct link. Pasted data and tokens are not sent anywhere.

JSON Formatter and Validator: Format, Minify, Sort Keys, Repair and Tree View

Paste JSON on the left; it is checked at once and errors point to the exact spot. If it is JavaScript-style JSON (comments, trailing commas) press "Repair to JSON". Nothing is uploaded.

Tree view

Regex Tester with Match Highlighting, Groups, Replace and a Plain-Language Explanation

Type the pattern (without the surrounding slashes) and paste test text. It uses the browser's regex engine, so results match what JavaScript will do, not PCRE or Python. A pattern that runs over 1.5 seconds is stopped so the page does not freeze.

Flags

Matched text

Matches

    Pattern explained

      JWT Decoder: View Header, Payload, Expiry and Verify the Signature (HS256 RS256 ES256)

      Paste a token (a leading "Bearer" is fine). Decoding only reads data that anyone can read; it does not prove the token is genuine. Only checking the signature with a key does, and the key box is below. Everything stays in your browser.

      Unix Timestamp Converter: Epoch to Date and Date to Epoch with Time Zones

      Enter a timestamp or a date and the other side appears at once. The unit is guessed from the size of the number (10 digits = seconds, 13 = milliseconds); you can set it yourself. A date without a zone uses the zone you selected.

      Now (seconds · ISO):

      ISO 8601 (selected zone)
      ISO 8601 (UTC)
      Readable date
      Relative to now
      Epoch seconds
      Epoch milliseconds
      ISO week · day of year
      Unit read as

      CSV to JSON and JSON to CSV Converter with Excel-Safe Thai Output

      Pick a direction and paste your data; the result appears at once. The delimiter is detected from the data (CSV from some regional Excel versions uses ; instead of ,). Nested JSON is spread into columns named a.b.c.

      Direction

      FAQ

      Why does my JSON fail when it looks right?

      The usual causes are single quotes (') instead of double ("), a comma after the last item, unquoted keys, or comments. Standard JSON allows none of them. Press "Repair to JSON" to fix them automatically.

      Do big numbers get corrupted?

      JSON.parse stores numbers as 64-bit floats, so integers beyond 15 to 16 digits can change. The tool warns when it sees one.

      Is my data uploaded?

      No. Everything runs in your browser.

      Is this the same as regex101?

      It uses the JavaScript (ECMAScript) engine in your browser, so it matches JavaScript and Node.js only. PHP, Python and Java differ in places, for example Python writes named groups as (?P<name>...).

      Why does it stop some patterns?

      Patterns such as (a+)+b against aaaa...ac take exponentially longer and can freeze a page. The engine runs in a separate Web Worker and is stopped after 1.5 seconds.

      Can \w match Thai?

      No. \w only matches A-Z a-z 0-9 _. Use \p{L} with the u flag to match Thai letters, for example [\p{L}\p{M}]+.

      Does decoding a JWT mean it is genuine?

      No. The header and payload are only Base64-encoded, so anyone can read them. Authenticity rests on the signature, which must be checked on the server with the secret or public key.

      Is it safe to paste a token here?

      The token never leaves your browser. Still, treat a live token like a password; use test or expired tokens when you can.

      Which algorithms can it verify?

      HS256/384/512, RS256/384/512 and ES256/384. PS* and EdDSA are not supported yet.

      What is a Unix timestamp?

      The number of seconds since 1 January 1970 00:00 UTC. Computers use it everywhere because it does not depend on a time zone.

      Why are some timestamps 13 digits long?

      They count milliseconds (JavaScript and Java do). Ten digits is seconds. The tool detects the unit from the size.

      Is Bangkok UTC+7 all year?

      Yes, Thailand has no daylight saving. The tool uses your browser's IANA time-zone database, which handles other countries' daylight saving correctly.

      Why does Thai look garbled when I open my CSV in Excel?

      Excel reads UTF-8 only if the file starts with a BOM. Tick "Add a BOM" when converting JSON to CSV, then download.

      What is CSV injection?

      If a cell starts with = + - or @, a spreadsheet may run it as a formula, which is dangerous when the data comes from someone else. The guard prefixes such cells with ' so they stay plain text.

      How is nested JSON turned into CSV?

      Into columns named a.b (objects) or a.0, a.1 (arrays). Columns are the union across all rows; a missing value is left empty.