Why must ads.txt be text/plain?

The IAB ads.txt specification requires Content-Type: text/plain. When a CDN or SPA fallback serves it as text/html, SSP crawlers treat the file as missing and your inventory is flagged unauthorised. Use Check a URL to confirm what your site actually serves.

Which MIME type should an HLS playlist use?

application/vnd.apple.mpegurl is Apple’s registered type; application/x-mpegURL is the legacy form and is still the most common in the wild. Players accept both. .ts segments should be video/mp2t — beware CDN rules that map .ts to TypeScript.

Does the URL check follow redirects?

Yes, up to five hops through the FizzKit relay, and the verdict is based on the final response. The relay only fetches public URLs and stores nothing.

How does file sniffing work?

The first 64 KB of the file are read in your browser and compared against known signatures (magic bytes). For text formats it falls back to heuristics like the XML root element, JSON parsing or #EXTM3U. Nothing is uploaded.

MIME Type Lookup

Search 250+ media types by extension, type or keyword and get an answer card with the exact Content-Type header to copy, charset and compression guidance, legacy aliases and serving gotchas (ads.txt must be text/plain, m3u8 as application/vnd.apple.mpegurl, text/javascript vs application/javascript, VAST as application/xml). Check a URL fetches any public resource through the FizzKit relay and compares the served Content-Type with what the extension and the body bytes say, with a plain-English verdict plus Content-Encoding, Cache-Control, Content-Length and CORS headers. File sniff identifies a dropped file from its magic bytes (PNG, JPEG, WebP, AVIF/HEIC, PDF, ZIP/Office/APK, gzip, MP4/M4A, WebM/MKV, MP3, WAV, OGG, WOFF/WOFF2, WASM, ELF, Mach-O, plus SVG/XML/HTML/JSON/VAST text heuristics) and flags it when the extension or the browser-declared type disagree.

Fetches URLs via the FizzKit relay — nothing is stored

MIME type	Extensions	Category	Flags	Description
application/atom+xml	.atom	application	utf-8gz	Atom feed.
application/avro	.avro	application		Apache Avro container file.
application/cbor	.cbor	application	gz	Concise Binary Object Representation (RFC 8949).
application/dash+xml	.mpd	application	utf-8gz!	MPEG-DASH Media Presentation Description manifest.
application/ecmascript	.es	application	utf-8gz	ECMAScript source (obsolete alias).
application/epub+zip	.epub	application		EPUB e-book.
application/feed+json	—	application	gz	JSON Feed.
application/geo+json	.geojson	application	gz	GeoJSON (RFC 7946).
application/gpx+xml	.gpx	application	utf-8gz	GPS Exchange Format.
application/graphql	.graphql .gql	application	utf-8gz!	Raw GraphQL query document (unofficial request type).
application/graphql-response+json	—	application	gz	GraphQL over HTTP response (current spec).
application/grpc	—	application		gRPC over HTTP/2 (length-prefixed protobuf frames).
application/gzip	.gz .tgz	application	!	Gzip archive.
application/importmap+json	.importmap	application	gz	JavaScript import map (usually inline, occasionally external).
application/java-archive	.jar .war .ear	application		Java archive (ZIP).
application/java-vm	.class	application	gz	Compiled Java class file.
application/javascript	.js .mjs	application	utf-8gz!	JavaScript source (legacy type; text/javascript is the standard).
application/jose	—	application		JWS / JWE compact serialisation.
application/json	.json .map	application	gz!	JavaScript Object Notation data.
application/json-patch+json	—	application	gz	RFC 6902 JSON Patch document.
application/jsonl	.jsonl	application	gz	JSON Lines (one JSON value per line).
application/jwk-set+json	—	application	gz	JSON Web Key Set (JWKS endpoint).
application/jwt	—	application		JSON Web Token (compact serialisation).
application/ld+json	.jsonld	application	gz	JSON-LD — linked-data JSON (schema.org structured data).
application/manifest+json	.webmanifest	application	gz!	Web App Manifest (PWA).
application/merge-patch+json	—	application	gz	RFC 7396 JSON Merge Patch.
application/mp4	.mp4s .m4p	application		ISO BMFF container without a specific audio/video role (CMAF init segments, protected content).
application/msgpack	.msgpack	application	gz	MessagePack binary serialisation.
application/msword	.doc .dot	application	gz	Microsoft Word 97–2003.
application/octet-stream	.bin .exe .dll .deb .dmg .iso .img .ipa	application	!	Arbitrary binary — the default when the type is unknown.
application/ogg	.ogx	application		Generic Ogg container.
application/pdf	.pdf	application	!	Adobe PDF document.
application/pgp-keys	.asc .gpg	application	gz	OpenPGP public/private key block.
application/pgp-signature	.sig .asc	application	gz	OpenPGP detached signature.
application/pkcs12	.p12 .pfx	application		PKCS #12 keystore.
application/pkcs8	.p8	application		PKCS #8 private key.
application/pkix-cert	.cer	application		PKIX certificate (DER).
application/postscript	.ps .eps .ai	application	gz	PostScript / Encapsulated PostScript / Illustrator.
application/problem+json	—	application	gz	RFC 9457 Problem Details for HTTP APIs.
application/protobuf	.pb .proto	application	gz!	Protocol Buffers binary payload.
application/rdf+xml	.rdf	application	utf-8gz	RDF/XML.
application/rss+xml	.rss	application	utf-8gz!	RSS feed.
application/rtf	.rtf	application	gz	Rich Text Format.
application/scim+json	—	application	gz	SCIM (System for Cross-domain Identity Management) payload.
application/soap+xml	—	application	utf-8gz	SOAP 1.2 envelope.
application/speculationrules+json	—	application	gz	Speculation Rules (prefetch/prerender) — Chrome.
application/toml	.toml	application	gz	TOML configuration (IANA-registered).
application/ttml+xml	.ttml .dfxp	application	utf-8gz	Timed Text Markup Language subtitles (IMSC, EBU-TT-D).
application/vast+xml	—	application	utf-8gz!	IAB VAST video ad document (unofficial; VAST responses are normally application/xml or text/xml).
application/vmap+xml	—	application	utf-8gz	IAB VMAP ad-break playlist (unofficial; usually application/xml).
application/vnd.amazon.ebook	.azw .azw3	application		Amazon Kindle e-book.
application/vnd.android.package-archive	.apk	application	!	Android APK package.
application/vnd.apache.arrow.file	.arrow .feather	application	gz	Apache Arrow IPC file.
application/vnd.apache.parquet	.parquet	application		Apache Parquet columnar data (IANA-registered 2024).
application/vnd.api+json	—	application	gz	JSON:API specification response.
application/vnd.apple.mpegurl	.m3u8	application	gz!	HLS playlist (Apple’s registered type).
application/vnd.apple.pkg	.pkg	application		macOS installer package.
application/vnd.debian.binary-package	.deb	application		Debian / Ubuntu package.
application/vnd.github+json	—	application	gz	GitHub REST API v3 media type.
application/vnd.google-earth.kml+xml	.kml	application	utf-8gz	Keyhole Markup Language (Google Earth).
application/vnd.google-earth.kmz	.kmz	application		Zipped KML.
application/vnd.ms-excel	.xls	application	gz	Microsoft Excel 97–2003.
application/vnd.ms-fontobject	.eot	application	gz	Embedded OpenType font (legacy IE).
application/vnd.ms-outlook	.msg	message	gz	Outlook message file.
application/vnd.ms-powerpoint	.ppt	application	gz	Microsoft PowerPoint 97–2003.
application/vnd.ms-sstr+xml	.ism .ismc	application	utf-8gz	Microsoft Smooth Streaming manifest.
application/vnd.oai.openapi	—	application	utf-8gz	OpenAPI document (YAML form).
application/vnd.oasis.opendocument.presentation	.odp	application		OpenDocument presentation.
application/vnd.oasis.opendocument.spreadsheet	.ods	application		OpenDocument spreadsheet.
application/vnd.oasis.opendocument.text	.odt	application		OpenDocument text (LibreOffice Writer).
application/vnd.openxmlformats-officedocument.presentationml.presentation	.pptx	application		Microsoft PowerPoint 2007+.
application/vnd.openxmlformats-officedocument.spreadsheetml.sheet	.xlsx	application		Microsoft Excel 2007+.
application/vnd.openxmlformats-officedocument.wordprocessingml.document	.docx	application	!	Microsoft Word 2007+.
application/vnd.rar	.rar	application		RAR archive (official IANA).
application/vnd.sqlite3	.sqlite .sqlite3 .db	application	gz	SQLite 3 database (IANA).
application/vnd.tcpdump.pcap	.pcap .cap	application	gz	Packet capture (tcpdump / Wireshark).
application/wasm	.wasm	application	gz!	WebAssembly binary module.
application/x-7z-compressed	.7z	application		7-Zip archive.
application/x-apple-diskimage	.dmg	application		macOS disk image.
application/x-bittorrent	.torrent	application	gz	BitTorrent metainfo file.
application/x-bzip2	.bz2	application		Bzip2 compressed archive.
application/x-elf	.elf .so .o	application	gz	ELF executable / shared object (Linux) — unofficial.
application/x-itunes-ipa	.ipa	application		iOS app archive (unofficial; usually served as octet-stream).
application/x-mach-binary	.dylib	application	gz	Mach-O binary (macOS / iOS) — unofficial.
application/x-mobipocket-ebook	.mobi .prc	application	gz	Mobipocket / Kindle e-book.
application/x-mpegURL	.m3u8	application	gz!	HLS playlist (legacy, still the most common in the wild).
application/x-msdownload	.exe .dll .msi	application	gz	Windows executable / installer (legacy).
application/x-ndjson	.ndjson	application	gz!	Newline-delimited JSON (streaming records).
application/x-pem-file	.pem .key	application	gz	PEM encoded crypto material.
application/x-rpm	.rpm	application		RPM package.
application/x-sh	.sh	application	utf-8gz	POSIX shell script.
application/x-shockwave-flash	.swf	application		Adobe Flash (obsolete; VPAID 1 Flash creatives).
application/x-subrip	.srt	application	utf-8gz	SubRip subtitles (unofficial).
application/x-tar	.tar	application	gz	Tape archive.
application/x-vpaid	—	application	gz	Not a real type — VPAID JS creatives are served as application/javascript with apiFramework="VPAID" in the VAST MediaFile.
application/x-www-form-urlencoded	—	application	gz!	Form-encoded key/value pairs (browser form POST).
application/x-x509-ca-cert	.crt .der	application		X.509 CA certificate (DER, legacy type).
application/x-xz	.xz	application		XZ / LZMA2 compressed archive.
application/x-yaml	.yaml .yml	application	utf-8gz	YAML — legacy unofficial type (most common).
application/xhtml+xml	.xhtml .xht	application	utf-8gz	XHTML (XML-serialized HTML).
application/xml	.xml .xsd	application	utf-8gz!	Generic XML.
application/xslt+xml	.xsl .xslt	application	utf-8gz	XSLT stylesheet.
application/yaml	.yaml .yml	application	gz!	YAML (IANA-registered 2024, RFC 9512).
application/zip	.zip	application		ZIP archive.
application/zstd	.zst	application		Zstandard compressed data.
audio/3gpp	.3ga	audio		3GPP audio-only container (AMR).
audio/aac	.aac	audio		Advanced Audio Coding (ADTS stream).
audio/amr	.amr	audio		Adaptive Multi-Rate speech codec.
audio/basic	.au .snd	audio	gz	Sun/NeXT µ-law audio.
audio/flac	.flac	audio		FLAC lossless audio.
audio/midi	.mid .midi	audio	gz	Standard MIDI file.
audio/mp4	.m4a .m4b .mp4a	audio	!	MP4 audio container (AAC / ALAC).
audio/mpeg	.mp3 .mp2 .mpga	audio	!	MP3 audio (MPEG-1 Layer 3).
audio/mpegurl	.m3u .m3u8	audio	utf-8gz	M3U playlist (audio streams; also used for audio-only HLS).
audio/ogg	.ogg .oga .spx	audio		Ogg Vorbis / Opus / Speex audio.
audio/opus	.opus	audio	!	Opus audio codec (Ogg-encapsulated .opus files).
audio/wav	.wav	audio	gz	Waveform Audio (PCM in a RIFF container).
audio/webm	.weba	audio		WebM audio (Opus / Vorbis).
audio/x-aiff	.aif .aiff .aifc	audio	gz	Audio Interchange File Format (Apple, uncompressed).
audio/x-ms-wma	.wma	audio		Windows Media Audio.
audio/x-scpls	.pls	audio	utf-8gz	PLS playlist (Shoutcast / Icecast).
audio/x-wav	.wav	audio	gz	Legacy WAV alias.
font/collection	.ttc	font	gz	TrueType / OpenType font collection.
font/otf	.otf	font	gz	OpenType font.
font/ttf	.ttf	font	gz	TrueType font.
font/woff	.woff	font	!	Web Open Font Format.
font/woff2	.woff2	font	!	Web Open Font Format v2 (preferred).
image/apng	.apng	image		Animated PNG.
image/avif	.avif	image	!	AV1 Image File Format.
image/avif-sequence	.avifs	image		Animated AVIF.
image/bmp	.bmp .dib	image	gz	Windows Bitmap.
image/gif	.gif	image	!	Graphics Interchange Format (animated banners, tracking pixels).
image/heic	.heic	image	!	High Efficiency Image Container (iPhone photos).
image/heic-sequence	.heics	image		HEIC image sequence (Live Photos, bursts).
image/heif	.heif	image		High Efficiency Image Format.
image/jp2	.jp2 .j2k	image	!	JPEG 2000.
image/jpeg	.jpg .jpeg .jpe .jfif	image	!	JPEG image.
image/jxl	.jxl	image	!	JPEG XL.
image/png	.png	image		Portable Network Graphics.
image/svg+xml	.svg .svgz	image	utf-8gz!	Scalable Vector Graphics.
image/tiff	.tif .tiff	image	!	Tagged Image File Format.
image/vnd.adobe.photoshop	.psd	image	gz	Adobe Photoshop document.
image/vnd.microsoft.icon	.ico	image	gz	Official IANA icon type.
image/webp	.webp	image		WebP image (Google).
image/x-icon	.ico	image	gz	Windows Icon — commonly used as favicon.
image/x-tga	.tga	image	gz	Truevision TGA.
message/http	—	message	gz	HTTP message (used by TRACE).
message/partial	—	message	gz	Partial message for fragmented email.
message/rfc822	.eml .mime	message	gz	Full email message.
model/gltf-binary	.glb	model	gz	3D model — glTF binary.
model/gltf+json	.gltf	model	gz	3D model — glTF text format.
model/obj	.obj	model	utf-8gz	Wavefront OBJ.
model/stl	.stl	model	gz	Stereolithography (3D printing).
model/vnd.usdz+zip	.usdz	model		Universal Scene Description (AR Quick Look on iOS).
multipart/alternative	—	multipart		Same content in alternative forms (text + HTML email).
multipart/byteranges	—	multipart		HTTP 206 response with multiple byte ranges.
multipart/form-data	—	multipart	!	HTML form file uploads. Each part has its own Content-Type.
multipart/mixed	—	multipart		Generic multipart MIME — different types per part (batch APIs).
multipart/related	—	multipart		Interrelated parts (MHTML, SOAP with attachments).
multipart/x-mixed-replace	—	multipart		Server push of replacing parts (MJPEG camera streams).
text/cache-manifest	.appcache	text	utf-8gz	HTML5 Application Cache manifest (removed from browsers).
text/calendar	.ics .ifb	text	utf-8gz!	iCalendar event / feed.
text/css	.css	text	utf-8gz!	Cascading Style Sheets.
text/csv	.csv	text	utf-8gz!	Comma-separated values.
text/event-stream	—	text	utf-8!	Server-Sent Events (SSE).
text/html	.html .htm .shtml	text	utf-8gz!	HTML document.
text/javascript	.js .mjs .cjs	text	utf-8gz!	JavaScript source (the standard type, RFC 9239).
text/jsx	.jsx	text	utf-8gz	JSX source (unofficial).
text/markdown	.md .markdown .mdown	text	utf-8gz!	CommonMark / GitHub Flavored Markdown.
text/n3	.n3	text	utf-8gz	Notation3 (N3) — RDF.
text/plain	.txt .text .log .ini .conf .cfg .ads.txt	text	utf-8gz!	Plain text.
text/tab-separated-values	.tsv .tab	text	utf-8gz	Tab-separated values.
text/turtle	.ttl	text	utf-8gz	Turtle — Terse RDF Triple Language.
text/uri-list	.uri .uris	text	utf-8gz	Newline-delimited URI list.
text/vcard	.vcf .vcard	text	utf-8gz	Contact card (vCard 4).
text/vtt	.vtt	text	utf-8gz!	WebVTT subtitles / captions.
text/x-c	.c .h .cpp .hpp .cc	text	utf-8gz	C / C++ source (unofficial).
text/x-component	.htc	text	utf-8gz	HTML Component (IE behaviours, obsolete).
text/x-diff	.diff .patch	text	utf-8gz	Unified diff / patch (unofficial).
text/x-go	.go	text	utf-8gz	Go source (unofficial).
text/x-handlebars-template	.hbs .handlebars	text	utf-8gz	Handlebars / Mustache template (used in inline <script type> tags).
text/x-java-source	.java	text	utf-8gz	Java source (unofficial).
text/x-less	.less	text	utf-8gz	Less stylesheet source (unofficial).
text/x-log	.log	text	utf-8gz	Log file (unofficial; usually text/plain).
text/x-php	.php	text	utf-8gz	PHP source (unofficial; served as text/html when executed).
text/x-python	.py .pyw	text	utf-8gz	Python source (unofficial).
text/x-ruby	.rb	text	utf-8gz	Ruby source (unofficial).
text/x-rust	.rs	text	utf-8gz	Rust source (unofficial).
text/x-sass	.sass	text	utf-8gz	Sass (indented) stylesheet source (unofficial).
text/x-scss	.scss	text	utf-8gz	SCSS stylesheet source (unofficial).
text/x-typescript	.ts .tsx .mts .cts	text	utf-8gz!	TypeScript source (unofficial).
text/x-yaml	.yaml .yml	text	utf-8gz	YAML (legacy text variant).
text/xml	.xml	text	utf-8gz!	XML (text subtype — equivalent to application/xml).
video/3gpp	.3gp .3gpp	video		3GPP mobile video.
video/3gpp2	.3g2	video		3GPP2 mobile video (CDMA).
video/av1	.av1 .obu	video		Raw AV1 bitstream (RTP payload).
video/h264	.h264 .264	video		Raw H.264 elementary stream (RTP payload type, RFC 6184).
video/iso.segment	.m4s	video	!	ISO BMFF media segment (DASH / CMAF / fMP4 HLS).
video/mp2t	.ts .m2ts .mts	video	!	MPEG-2 Transport Stream (HLS segments).
video/mp4	.mp4 .m4v .mp4v .mpg4	video	!	MPEG-4 video (H.264 / H.265 / AV1 in an ISO BMFF container).
video/mpeg	.mpg .mpeg .mpe .m1v .m2v	video		MPEG-1 / MPEG-2 program stream.
video/ogg	.ogv	video		Ogg video (Theora).
video/quicktime	.mov .qt	video	!	QuickTime video.
video/vnd.dlna.mpeg-tts	.ts .tts	video		MPEG-2 TS (DLNA registration) — IIS default for .ts.
video/webm	.webm	video	!	WebM video (VP8 / VP9 / AV1 in a Matroska-derived container).
video/x-flv	.flv	video		Flash Video (obsolete; still emitted by RTMP tooling).
video/x-matroska	.mkv .mk3d	video	!	Matroska video.
video/x-mpegurl	.m3u8	video	utf-8gz	M3U playlist (video variant, non-standard).
video/x-ms-wmv	.wmv	video		Windows Media Video.
video/x-msvideo	.avi	video		AVI video (RIFF).

Total types

210

Showing

210

HTTP Status Codes

Searchable reference for every HTTP status code.

URL Parser & Query Editor

Break any URL into parts, edit query params live, unwrap nested redirect URLs, decode ad macros, build UTMs and follow redirects.

HTTP Request Tester

Send GET, POST, PUT and other requests to any public URL and inspect status, headers, body, redirects and timing.

How to use MIME Type Lookup

1Type an extension (png, .m3u8, ads.txt), a full type (application/json) or a keyword — the answer card shows the exact Content-Type line to copy with charset and compression notes.
2Filter the table by category and click any row to open its card; legacy aliases and serving gotchas appear underneath.
3Open Check a URL, paste any public URL and press Check: the tool reports the served Content-Type, the type expected from the extension, a body sniff and a verdict such as "ads.txt served as text/html".
4Open File sniff and drop a file to identify it by magic bytes and compare against its extension and the browser-declared type.
5Share a lookup with ?q=<extension> in the URL.

About MIME Type Lookup

MIME Type Lookup is part of FizzKit — a collection of focused developer and ad-tech tools. This tool uses the FizzKit relay to fetch public URLs on your behalf (so browser CORS rules do not get in the way); fetched content is returned to your browser and not stored.

Frequently asked questions

RFC 9239 (2022) made text/javascript the single standard type and marked application/javascript obsolete. Browsers accept both, but ES modules and workers require one of the JavaScript types — text/plain fails with a strict MIME type error.

Related tools