Add or remove a UTF-8 BOM

How to use it

1. Drag your .txt files onto the area above, or press "Choose files".
2. If options are shown, set them as you like. They appear below the file list.
3. Press "Convert". The conversion runs on your device, shows its progress and can be cancelled at any time.
4. Press "Download" next to a result. With several results, "Download all as ZIP" gets them in one go.

The formats involved

Limits and things to watch for

• The file size that can be processed depends on your device. The limit for your device is shown in the drop area, and files above it are refused with a message.

FAQ

Sources and check date

• QOI specification 1.0 (qoiformat.org)
  14-byte header (magic qoif, big-endian width/height, channels 3|4, colorspace 0|1), 8-byte end marker, un-premultiplied alpha · 2026-11-10
• Netpbm: PPM format specification
  Magic numbers P3 (plain) / P6 (raw); Maxval below 65536; 2 bytes per sample when Maxval >= 256 · 2026-11-10
• Microsoft Learn: Bitmap Header Types
  BITMAPINFOHEADER / BITMAPV4HEADER; RedMask/GreenMask/BlueMask valid with BI_BITFIELDS; bottom-up rows padded to 4 bytes · 2026-11-10
• WebP Container Specification
  ANMF chunk (blending/disposal bits), VP8X flags, ANIM loop count · 2026-11-10
• POSIX pax / ustar (Open Group Base Specifications Issue 7)
  pax interchange format, extended header records (path, mtime, size) · 2026-11-10
• EPUB 3.3 (W3C Recommendation), OCF ZIP container
  4.2.2 reserves the file name mimetype; 4.3 ZIP requirements (section 4.3 body not read) · 2026-11-10
• W3C: WebVTT: The Web Video Text Tracks Format (Candidate Recommendation Draft 20 May 2026)
  File body: UTF-8, MIME text/vtt, optional BOM, "WEBVTT" line; timestamp: hours optional (required if non-zero), mm:ss.ttt with FULL STOP; cue text may contain character references · 2026-11-10
• NDJSON - Newline delimited JSON 1.0.0
  one JSON value per line · 2026-11-10
• JSON Lines
  UTF-8, one JSON value per line · 2026-11-10
• GitHub Flavored Markdown Spec: tables (extension)
  header row, delimiter row, pipe escaping · 2026-11-10
• Java SE 21 java.util.Properties
  load(): line continuation, comments, escapes; ISO 8859-1 and Unicode escapes · 2026-11-10
• python-dotenv README (file format)
  export directive, quoting, allowed escape sequences, comments · 2026-11-10
• RFC 7519 JSON Web Token
  JWT structure, registered claims exp / nbf / iat · 2026-11-10
• RFC 4648 Base16, Base32, Base64 Encodings
  Base64, Base64URL, Base16 · 2026-11-10
• RFC 3986 URI Generic Syntax
  percent-encoding, reserved and unreserved characters · 2026-11-10
• National Institute of Korean Language: Romanization of Korean
  basic principles, transcription system, special provisions and the example words used in our tests · 2026-11-10
• HTML Standard: named character references
  entity list incl. legacy names without semicolon · 2026-11-10
• Unicode Standard Annex #15 Normalization Forms
  NFC, NFD, NFKC, NFKD · 2026-11-10

Date we opened the original documents ourselves: 2026-11-10. Specifications can change, so read the original again before anything important.