Hex Editor

Every file is a sequence of bytes, and most tools hide them from you. A hex editor shows them as they are: two hexadecimal digits per byte, with the matching characters beside them. That is the quickest way to answer questions such as “does this file really start with a PNG header?”, “where does this string sit?” and “what number is stored at offset 0x24?”. This editor runs in your browser, so a private file never leaves your machine.

Reading the layout

Each row starts with an offset, the position of its first byte counted from zero and written in hexadecimal. Sixteen bytes follow on a wide screen (eight below 640 pixels, so a phone does not scroll sideways), then the same bytes as text. A byte in the printable ASCII range 0x20 to 0x7E appears as its character, anything else as a dot. Pages of the dump are reached with the previous and next buttons, or by typing an offset into the jump box, which accepts decimal or a 0x prefix.

The built-in sample

The Sample button loads a 315-byte file. Its first rows hold readable text, “OpenWorkstand hex editor sample file”, followed by three small control bytes 00 01 02, and then the sentence “magic 89 50 4E 47” written as text. After that comes a run of every byte value from 00 up to FF in order, so you can see the whole range of bytes, printable and not, in a few rows: the text column fills with letters and punctuation in the middle of the run and with dots elsewhere. Select any byte and the inspector shows it as an unsigned and signed 8-bit number, then as 16, 32 and 64-bit integers and floats where enough bytes remain.

Editing and searching

Click a value, type two hex digits and the byte changes; edited bytes are drawn bold so you can see what you touched, and “Undo all edits” restores the original. Searching accepts either hex bytes, such as 89 50 4E 47, or plain text, and “Find next” moves through the matches. When you are done, “Download edited file” saves a copy; your original on disk is not modified.

Byte order and the inspector

Multi-byte numbers can be stored with the least significant byte first (little-endian, used by x86 and ARM in their usual modes) or most significant first (big-endian, used in network protocols and many file headers such as PNG). The inspector shows both readings of the bytes at the cursor so you can tell which one a format uses: if a 4-byte length reads as 13 in big-endian and 218,103,808 in little-endian, the format is big-endian.

Limits

The editor holds the whole file in memory, so it refuses files above 16 MB. It replaces bytes but does not insert or delete them, because that would shift every offset after the change. It does not understand file formats, so checksums and length fields inside a file are not repaired when you change the data they cover.

Related tools

• File Type Identifier names a file’s format from its first bytes.
• Hex to Binary converts the values you read from a dump.
• XOR Calculator is useful when bytes in a file look obfuscated.
• CRC Calculator recalculates the checksum of an edited block.