(registered 2026-10-06, last updated 2026-10-06)

Media type name: application

Media subtype name: vnd.dai

Required parameters: N/A

Optional parameters: N/A

Encoding considerations: binary

The file is a sectioned container: a header, a section table, page-aligned sections holding a JSON manifest, a zip archive of the application, and a SQLite database, and a 64-byte footer. The footer carries a generation counter and the SHA-256 of the database section.

Security considerations:

A DAI container carries executable content: an HTML application intended to run only inside a host that applies the isolation defined in §4 of the specification (an opaque-origin sandboxed frame under a Content Security Policy permitting no network connection). The specification requires that a host not applying that isolation does not execute the content.

The container is a sectioned binary file holding a JSON manifest, a zip archive of the application, and a SQLite database. The manifest carries SHA-256 digests of every archive entry and may carry an ECDSA P-256 signature over them in a COSE_Sign1 envelope. The specification requires a host to verify every digest before running anything and to verify the signature when a key is present (§7). The signature covers the manifest and the application, not the database; the database section is verified separately against a SHA-256 digest held in the file's footer (§2). Verification establishes that the file is unchanged since it was signed, not the identity of the signer; §8 and §9.6 describe what a host may claim about a publisher.

Because the archive is inflated before its manifest can be checked, the specification requires a reader to bound decompression in advance — a limit on the bytes produced for any one entry, on the total across entries, and on the number of entries — refusing rather than allocating when a declared size, the declared total, or the entry count exceeds that limit, and stopping if an entry inflates past the size it declares (§7). The manifest contains no active content.

The application may read and write the SQLite database. The format grants it no capability to reach the network, the filesystem beyond the file itself, or other origins.

Privacy: the file may contain personal data the application stored. It contains no tracking, and the specification requires that a host send nothing when opening a file.

Interoperability considerations:

The format is versioned by the manifestVersion field in the manifest. A reader accepts the versions it implements and refuses others, reporting a refusal that tells the person to update the host (§9.1). The specification defines versions 2 and 3. A conformance suite and an independent reference reader in Python are published with the specification.

Published specification: DAI Container Format v0.2, §2 (the sectioned form), §7 (verification), and §9 (manifestVersion 3): https://github.com/dynamicapplicationinterface/dai-core/blob/main/docs/spec-v0.2.md

Applications which use this media: The DAI opener (https://opendai.app), the DAI desktop application, and the dai command line tool; any host implementing the specification.

Fragment identifier considerations: N/A

Restrictions on usage: N/A

Additional information:

Deprecated alias names for this type: N/A
Magic number(s): the first four bytes are "DAI" followed by a NULL byte (0x44 0x41 0x49 0x00)
File extension(s): .dai
Macintosh file type code: N/A
Object Identifiers: N/A

Other Information & Comments: N/A

Person to contact for further information:

Name: Christopher Whitlow
Email: info&dynamicapplicationinterface.io

Intended usage: COMMON

Author/Change controller: Christopher Whitlow / Dynamic Application Interface Opensource Project