What is MIME type "image/heif-sequence"?

A MIME type is a string that tells browsers and other tools how to handle a particular kind of file.

image/heif-sequence is a MIME type that designates files storing a sequence of images encoded in the High Efficiency Image File Format (HEIF).
It enables multiple frames—such as those from burst shots or live photos—to be contained in one file while keeping file sizes small and quality high.

Main use case: Storing animated or sequential images in a single container.
Efficiency: Uses advanced compression methods to save space without major quality loss.
Supports applications in digital photography and modern mobile devices.

Files using this format are commonly seen as HEIC or HEIF types.
For more technical details, check the information on Wikipedia.

Associated file extensions

.heic, .heif

Usage Examples

HTTP Header

When serving content with this MIME type, set the Content-Type header:


    Content-Type: image/heif-sequence

HTML

In HTML, you can specify the MIME type in various elements:


    <a href="file.dat" type="image/heif-sequence">Download file</a>

Server-side (Node.js)

Setting the Content-Type header in Node.js:


    const http = require('http');    
    
    http.createServer((req, res) => {    
      res.setHeader('Content-Type', 'image/heif-sequence');    
      res.end('Content here');    
    }).listen(3000);

Associated file extensions

.heic, .heif

FAQs

What is the difference between image/heif and image/heif-sequence?

While image/heif is typically used for single still images, image/heif-sequence explicitly designates a file containing a series of images, such as a burst shot or an animation. Both types commonly share the .heic or .heif extensions, relying on the MIME type or internal metadata to distinguish behavior.

Which browsers natively support image/heif-sequence?

Native support is currently limited primarily to Apple Safari on macOS and iOS. Major browsers like Chrome, Firefox, and Edge do not natively render HEIF sequences; for web usage, it is recommended to convert these files to widely supported formats like animated WebP or MP4.

How do I configure Apache to serve HEIF sequences?

You can enable support by adding the correct directive to your .htaccess file or server config. Add the line AddType image/heif-sequence .heic .heif to ensure the web server sends the correct Content-Type header to the client.

How do I add image/heif-sequence support to Nginx?

Edit your mime.types file (often found in /etc/nginx/) and include the line image/heif-sequence heic heif;. After saving, run sudo nginx -s reload to apply the configuration so that files with these extensions are served with the correct MIME type.

Why can't I open image/heif-sequence files on Windows?

Windows 10 and 11 require the HEIF Image Extensions package from the Microsoft Store to decode these files natively in the Photos app. Without this extension, the OS does not recognize the encoding, though third-party tools like VLC or GIMP may still open them.

Is image/heif-sequence considered a video format?

Technically, no; it is a container for multiple still images encoded with HEVC, similar to how an animated GIF works but with much better compression. While it appears as a video during playback (like in Apple Live Photos), it is structured as a sequence of discrete image items.

Should I use image/heif-sequence for website animations?

Due to poor cross-browser compatibility, it is not recommended for general web use. Instead, consider using animated AVIF or WebP, which offer similar compression benefits but have significantly better support across modern web browsers.

General FAQ

What is a MIME type?

A MIME (Multipurpose Internet Mail Extensions) type is a standard that indicates the nature and format of a document, file, or assortment of bytes. MIME types are defined and standardized in IETF's RFC 6838.

MIME types are important because they help browsers and servers understand how to process a file. When a browser receives a file from a server, it uses the MIME type to determine how to display or handle the content, whether it's an image to display, a PDF to open in a viewer, or a video to play.

MIME types consist of a type and a subtype, separated by a slash (e.g., text/html, image/jpeg, application/pdf). Some MIME types also include optional parameters.

How do I find the MIME type for a file?

You can check the file extension or use a file identification tool such as file --mime-type on the command line. Many programming languages also provide libraries to detect MIME types.

Why are multiple MIME types listed for one extension?

Different applications and historical conventions may use alternative MIME identifiers for the same kind of file. Showing them all helps ensure compatibility across systems.