(registered 2022-04-05, last updated 2022-04-05) Media type name: application Media subtype name: fdf Required parameters: None Optional parameters: None Encoding considerations: binary Security considerations: FDF is used to carry form and annotation data in both directions, such as between a client and a server. As such, its security implications are dependent on what use that data is put to at both the client and the server ends. At the client, the FDF data is usually combined with a PDF file and presented to an end user in some form. At the server, that data can be stored in databases, or fed to other applications. In all cases, it is important that this data is scrutinized to prevent malicious inputs from causing damage. Unlike PDF, FDF files cannot be digitally signed or protected. FDF does not natively support encryption. However it is possible to encrypt an entire FDF file (by treating it is a binary blob) and then to embed that entire encrypted blob into the EncryptedFDFs array entry of another (wrapper) FDF. Encryption used by FDF for EncryptedFDFs is old and limited to a weak 40-bit RC4 using MD5 hash and is thus not recommended. The FDF EncryptedFDFs entry is explicitly marked as deprecated from PDF 2.0 (ISO 32000-2:2020). As FDF is based on PDF, it is extensible, can contain binary data or other formats - see RFC 8118 for additional considerations about PDF security. Interoperability considerations: Only a single version of FDF has ever been defined, which is version 1.2 that was introduced with PDF 1.2. The versioning mechanism used by FDF is the same as that for PDF. As described in clause 12.7.8 of ISO 32000-2:2020, the first header line of an FDF file contains the FDF version number which may then be overriden by the Version key of the FDF catalog dictionary, should future versions be defined. See also RFC 8118 for additional general considerations on PDF interoperability. Published specification: The Forms Data Format (FDF) is defined in clause 12.7.8 in "ISO 32000-2:2020. Document management - Portable document format — Part 2: PDF 2.0": https://www.iso.org/standard/75839.html. Applications which use this media: The Forms Data Format (FDF) is a file format used for interactive form and annotation data since PDF 1.2. FDF can be used when submitting form data to a server, receiving the response, and incorporating it into an interactive form. It can also be used to export form and annotation data to stand-alone files that can be stored, transmitted electronically, and imported back into PDF files. FDF is entirely based on PDF - it uses the same syntax and has essentially the same file layout and structure. Fragment identifier considerations: FDF itself does not have fragment identifiers, but may be the target of a PDF fragment identifier. Annex O of ISO 32000-2:2020 defines all PDF related fragment identifiers. Table Annex O.4 defines the "fdf" PDF open parameter which takes a relative or absolute URI argument to an FDF file. This opens the PDF document and then imports data from the specified FDF file. This information is also described informatively in RFC 8118. Restrictions on usage: None Additional information: 1. Deprecated alias names for this type: application/vnd.fdf 2. Magic number(s): As per clause 12.7.8 in ISO 32000-2:2020, all FDF files start with the characters "%FDF-" followed by the FDF version number, e.g., "%FDF-1.2". These characters are in US-ASCII encoding. 3. File extension(s): .fdf 4. Macintosh file type code: n/a 5. Object Identifiers: n/a General Comments: FDF is standardized by ISO Technical Committee 171 Sub-Committee 2 Working Group 8. Person to contact for further information: 1. Name: Betsy Fanning 2. Email: betsy.fanning&pdfa.org Intended usage: Common The Forms Data Format (FDF) is a file format used for PDF form and annotation data. Author/Change controller: Committee Manager for ISO TC 171 SC 2, info&pdfa.org