Web
Cascading Style Sheets is a web format commonly identified by .css. Use the listed signatures, MIME types, and structure notes to validate files beyond the extension.
3A 72 6F 6F 74 :rootSIGNATURE = bytes.fromhex("3a726f6f74")
OFFSET = 0
def is_css(path: str) -> bool:
with open(path, "rb") as f:
f.seek(OFFSET)
head = f.read(len(SIGNATURE))
return head == SIGNATUREconst SIGNATURE = [0x3a, 0x72, 0x6f, 0x6f, 0x74];
const OFFSET = 0;
// bytes: a Uint8Array / Buffer holding the start of the file
export function isCss(bytes) {
return SIGNATURE.every((byte, i) => bytes[OFFSET + i] === byte);
}package fileid
import "bytes"
var iscssSignature = []byte{0x3a, 0x72, 0x6f, 0x6f, 0x74}
const iscssOffset = 0
func IsCss(b []byte) bool {
end := iscssOffset + len(iscssSignature)
if len(b) < end {
return false
}
return bytes.Equal(b[iscssOffset:end], iscssSignature)
}const SIGNATURE: &[u8] = &[0x3a, 0x72, 0x6f, 0x6f, 0x74];
const OFFSET: usize = 0;
fn is_css(bytes: &[u8]) -> bool {
bytes.get(OFFSET..OFFSET + SIGNATURE.len()) == Some(SIGNATURE)
}<?php
$signature = "\x3a\x72\x6f\x6f\x74";
$offset = 0;
function is_css(string $bytes): bool {
global $signature, $offset;
return substr($bytes, $offset, strlen($signature)) === $signature;
}Cascading Style Sheets is used for data exchange, imports, exports, parser testing, and validation workflows. Encoding, delimiters, versions, and container structure often change implementation behavior.
Untrusted input is not safe just because the format was detected. Account for parser exceptions, large files, unexpected encodings, and external references.
11 samples help test leading-byte detection, parser errors, upload limits, and download behavior.
Blue Sky CSS is a Cascading Style Sheets sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
01-blue-sky.cssb21610d64e082151dc6ed6e7fd77450273ea197fb932a44e482c672a2da94104Flower Garden CSS is a Cascading Style Sheets sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
02-flower-garden.css2b4049937e2555e3b406fd4044f7edf0e2c91a9cc6426dddeace122629fb8c1cNavy Blue Sky CSS is a Cascading Style Sheets sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
03-navy-blue-sky.css2e8a93482737980e961e069d7f29cbaf01fc59ba6e2522eadb31c2f377c21526Nature of the Sky CSS is a Cascading Style Sheets sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
04-nature-sky.cssc8e6062864bb2217599509009a338f85ac5d02566748041eb62f754f51e53a98Sky Landscape CSS is a Cascading Style Sheets sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
05-sky-landscape.cssea49ce1bcb735e7455d02c353cc714dcd2e818c396f78822b369a6e12dc6aad2Starry Sky CSS is a Cascading Style Sheets sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
06-starry-sky.css2ad5ab74d78a3d2ad64dcadf71ce84bbb9441b725ed1567729621c02f1f0eff2Blue Night Sky CSS is a Cascading Style Sheets sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
07-blue-night-sky.cssd86e9bfcb4e2222f00bfe6f4da35ac36c71010b54c27f781e30aa010c5682182Hibiscus Flower CSS is a Cascading Style Sheets sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
08-hibiscus-flower.css02502ed584ef0a1ac98ddef81ca2790a25f59d0a0dce93a17f217f64822b7116Arctic Sky CSS is a Cascading Style Sheets sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
09-arctic-sky.css24134d3d61947d2d723d194ea3d15bd4fa3c833f35c4b742bb9373c5aad0915eSunset Rays CSS is a Cascading Style Sheets sample based on Wikimedia Commons. It can be used to test downloads, parsers, previews, and file type detection.
10-sunset-rays.css0910c9d5df680cc91dffa4eb06c9c3adab01be40d5207cc27a5bcef622f27260NASA Blue Marble CSS is a Cascading Style Sheets 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.css87fbbe9ca50740d45f6bea5c1672b5c1ecb728c9291f20eb57641e07a5afc6fdCascading Style Sheets files begin with the byte signature 3A 72 6F 6F 74 (":root"). Detect the format by reading these leading bytes rather than trusting the file extension alone.
The MIME type for Cascading Style Sheets is text/css.
Cascading Style Sheets files use the .css extension. The extension is a convention only and does not guarantee the file contents, so combine it with signature and structure checks.