Byte Order Mark (BOM) Detector

A Byte Order Mark (BOM) is a Unicode special character (U+FEFF ZERO WIDTH NO-BREAK SPACE) placed at the beginning of a text file or stream to indicate the encoding type and byte order (endianness) of the data. The BOM acts as a signature that helps software correctly interpret the encoding of the text that follows. For UTF-16 and UTF-32 encodings, the BOM specifically identifies whether the bytes are in big-endian (most significant byte first) or little-endian (least significant byte first) order. While UTF-8 does not have endianness, its BOM (EF BB BF) is commonly used by Windows applications to mark files as UTF-8 encoded. Our Byte Order Mark Detector reads the first bytes of any file and compares them against a comprehensive database of known BOM signatures to instantly identify the encoding.

1. Binary Data Reading: The BOM detector reads the raw bytes from your uploaded file or encodes your pasted text into bytes using UTF-8 encoding. Only the first 16 bytes are needed for accurate BOM detection, making the process extremely fast even for very large files.
2. BOM Signature Matching: The detector compares the initial bytes against all known BOM signatures including UTF-8 (EF BB BF), UTF-16 BE (FE FF), UTF-16 LE (FF FE), UTF-32 BE (00 00 FE FF), UTF-32 LE (FF FE 00 00), UTF-7 (2B 2F 76 38), SCSU (0E FE FF), BOCU-1 (FB EE 28), and GB-18030 (84 31 95 33). Multiple matches are reported when applicable.
3. Results Presentation: The detector displays a clear verdict, a color-coded hex dump with highlighted BOM bytes, detailed encoding information including endianness and byte length, and a complete reference table of all known BOM signatures for educational purposes.

• Encoding Type: The detector identifies the Unicode encoding standard being used - UTF-8, UTF-16 (with endianness), UTF-32 (with endianness), or other legacy Unicode encodings like UTF-7, SCSU, or BOCU-1.
• Endianness: For multi-byte encodings like UTF-16 and UTF-32, the detector determines whether the bytes are in big-endian (network order) or little-endian order, which is critical for correct interpretation of the text data.
• Hex Sequence: The exact hexadecimal byte sequence of the detected BOM is displayed alongside a visual hex dump of the first 16 bytes, with the BOM bytes highlighted for easy identification.
• Byte-Level Analysis: The detector shows the raw hexadecimal and ASCII representation of the file's opening bytes, helping you understand the binary structure regardless of whether a BOM is present.

Your privacy is paramount. Our BOM detector performs all analysis entirely within your browser using JavaScript - no file data is uploaded to any server, and nothing leaves your device. This ensures sensitive documents and proprietary data remain completely confidential. The detector is 100% free with no file size limits (only the first 16 bytes are read for analysis). Note that while a BOM helps identify encoding, not all files have one - many UTF-8 files, especially on Unix/Linux systems, omit the BOM intentionally. Tools and scripts should handle both BOM and BOM-less files gracefully for maximum compatibility across platforms.