Document
Excel Open XML Workbook is a document format commonly identified by .xlsx. Use the listed signatures, MIME types, and structure notes to validate files beyond the extension.
50 4B 03 04 PK..SIGNATURE = bytes.fromhex("504b0304")
OFFSET = 0
def is_xlsx(path: str) -> bool:
with open(path, "rb") as f:
f.seek(OFFSET)
head = f.read(len(SIGNATURE))
return head == SIGNATUREconst SIGNATURE = [0x50, 0x4b, 0x03, 0x04];
const OFFSET = 0;
// bytes: a Uint8Array / Buffer holding the start of the file
export function isXlsx(bytes) {
return SIGNATURE.every((byte, i) => bytes[OFFSET + i] === byte);
}package fileid
import "bytes"
var isxlsxSignature = []byte{0x50, 0x4b, 0x03, 0x04}
const isxlsxOffset = 0
func IsXlsx(b []byte) bool {
end := isxlsxOffset + len(isxlsxSignature)
if len(b) < end {
return false
}
return bytes.Equal(b[isxlsxOffset:end], isxlsxSignature)
}const SIGNATURE: &[u8] = &[0x50, 0x4b, 0x03, 0x04];
const OFFSET: usize = 0;
fn is_xlsx(bytes: &[u8]) -> bool {
bytes.get(OFFSET..OFFSET + SIGNATURE.len()) == Some(SIGNATURE)
}<?php
$signature = "\x50\x4b\x03\x04";
$offset = 0;
function is_xlsx(string $bytes): bool {
global $signature, $offset;
return substr($bytes, $offset, strlen($signature)) === $signature;
}Excel Open XML Workbook is used for data exchange, imports, exports, parser testing, and validation workflows. Encoding, delimiters, versions, and container structure often change implementation behavior.
Document formats may include scripts, attachments, macros, or external references. Sandbox previews and conversions, and avoid opening untrusted files directly.
11 samples help test leading-byte detection, parser errors, upload limits, and download behavior.
Blue Sky XLSX is a Excel Open XML Workbook sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
01-blue-sky.xlsxa63033e487d09762113edfc3457c25a2be33ce188b59f4693c5cdc513b9eeee5Flower Garden XLSX is a Excel Open XML Workbook sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
02-flower-garden.xlsxb3fefd4bf0b8361ba7cb5c42745299b83cdbc04d8609f1376805d6e9725b7549Navy Blue Sky XLSX is a Excel Open XML Workbook sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
03-navy-blue-sky.xlsx5d6c61220a1e37f2ba1d4daa14179eb59601261d9014df156bc63ce7b52412bdNature of the Sky XLSX is a Excel Open XML Workbook sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
04-nature-sky.xlsxd839aa08700f3d784c642a107af94f1211eb69e57292ebbe9b917da0588c7acbSky Landscape XLSX is a Excel Open XML Workbook sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
05-sky-landscape.xlsx08fd69577c2f30e7a875651effabb62b692e4e10b50a0ed1b7f7bcaea420bd8fStarry Sky XLSX is a Excel Open XML Workbook sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
06-starry-sky.xlsx5635d4b0aad8e7119b389cf674bbd5da70f25f091ca85faaaef511d27dccb967Blue Night Sky XLSX is a Excel Open XML Workbook sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
07-blue-night-sky.xlsx09cfab13e1ef99e9f2f0dc720994bcfa3cdbc2ac5b5d9bbb3631dde629d1798aHibiscus Flower XLSX is a Excel Open XML Workbook sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
08-hibiscus-flower.xlsx70fe0048159a8a53888680c317f584f0416c5f7b55e34b5fe841e0a1e7f509ecArctic Sky XLSX is a Excel Open XML Workbook sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
09-arctic-sky.xlsx2fecd636573dfe5cb647582e0a9427ab2533fdf296f7dc98cd0b223d3af8eaeaSunset Rays XLSX is a Excel Open XML Workbook sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
10-sunset-rays.xlsx3de15266ebe3b007c7b561d935ca1d2fa4b30c46868273d0349a269cdb6cd13eNASA Blue Marble XLSX is a Excel Open XML Workbook sample based on NASA Image and Video Library. It can be used to test downloads, parsers, previews, and file type detection.
nasa-blue-marble-2012-east.xlsx6b8bfb03a1846eb39c9ac9b80967304bf63905802d74d45f322eacad8d93c080Excel Open XML Workbook files begin with the byte signature 50 4B 03 04 ("PK.."). Detect the format by reading these leading bytes rather than trusting the file extension alone.
The MIME type for Excel Open XML Workbook is application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.
Excel Open XML Workbook files use the .xlsx extension. The extension is a convention only and does not guarantee the file contents, so combine it with signature and structure checks.