JMAP File Storage extension

1.1. Conventions Used in This Document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶

2.1. urn:ietf:params:jmap:filenode

The capability urn:ietf:params:jmap:filenode being present in the "accountCapabilities" property of an account represents support for the FileNode datatype. Servers that include the capability in one or more "accountCapabilities" properties MUST also include the property in the "capabilities" property.¶

The value of this property in the JMAP session "capabilities" property MUST be an empty object.¶

The value of this property in an account's "accountCapabilities" property is an object that MUST contain the following information on server capabilities and permissions for that account:¶

• maxFileNodeDepth: "UnsignedInt|null"¶

  The maximum depth of the FileNode hierarchy (i.e., one more than the maximum number of ancestors a FileNode may have), or null for no limit.¶

• maxSizeFileNodeName: "UnsignedInt"¶

  The maximum length, in (UTF-8) octets, allowed for the name of a FileNode. This MUST be at least 100, although it is recommended servers allow more.¶

• forbiddenNameChars: "String|null"¶

  A string where each character is forbidden in FileNode names. If null, the server does not restrict name characters beyond the requirement that names be non-empty Net-Unicode strings. The server MUST reject names containing any of these characters with an "invalidProperties" error.¶

• forbiddenNodeNames: "String[]|null"¶

  An array of complete names that the server will not accept as FileNode names, compared case-insensitively. For example, [".", "..", "CON", "PRN", "AUX", "NUL"] would forbid common path-traversal names and Windows reserved device names. If null, the server does not forbid any specific names.¶

• fileNodeQuerySortOptions: "String[]"¶

  A list of all the values the server supports for the "property" field of the Comparator object in a "FileNode/query" sort (see "FileNode/query" below). This MAY include properties the client does not recognise (for example, custom properties specified in a vendor extension). Clients MUST ignore any unknown properties in the list.¶

• mayCreateTopLevelFileNode: "Boolean"¶

  If true, the user may create a FileNode (see "FileNode/set" below) in this account with a null parentId. (Permission for creating a child of an existing FileNode is given by the "myRights" property on that FileNode.)¶

• webTrashUrl: "String|null"¶

  The URL at which the folder with the "trash" role can be viewed on the web. If null, there is no web URL available.¶

• caseInsensitiveNames: "Boolean"¶

  If true, the server treats file names as case-insensitive for all name collision checks, including the sibling uniqueness constraint and onExists handling. The server preserves the original case as provided by the client.¶

• webUrlTemplate: "String|null"¶

  A template by which any node can be viewed on the web, in URI Template (level 1) format [URI-TEMPLATE]. The available variable is {id}, which is the FileNode id. If null, there is no web URL available.¶

• webWriteUrlTemplate: "String|null"¶

  A URI Template (level 1) [URI-TEMPLATE] for writing content to a file node. The available variable is {id}, which is the FileNode id. If null, direct HTTP writes are not supported and clients must use FileNode/set to update content. See "Direct HTTP Write" below for the HTTP semantics.¶

{
  "urn:ietf:params:jmap:filenode": {
    "maxFileNodeDepth": 50,
    "maxSizeFileNodeName": 255,
    "fileNodeQuerySortOptions": [
      "name", "type", "size", "created", "modified",
      "nodeType", "tree"
    ],
    "forbiddenNameChars": "/<>:\"\\|?*",
    "forbiddenNodeNames": [".", "..", "CON", "PRN", "AUX",
      "NUL", "COM0", "COM1", "COM2", "COM3", "COM4", "COM5",
      "COM6", "COM7", "COM8", "COM9", "LPT0", "LPT1", "LPT2",
      "LPT3", "LPT4", "LPT5", "LPT6", "LPT7", "LPT8", "LPT9"
    ],
    "caseInsensitiveNames": false,
    "mayCreateTopLevelFileNode": false,
    "webTrashUrl": "https://files.example.com/trash",
    "webUrlTemplate": "https://files.example.com/view/{id}",
    "webWriteUrlTemplate": "https://files.example.com/write/{id}"
  }
}

3.1. FileNode objects

The filenode object has the following keys:¶

• id: "Id" (immutable; server-set)¶

  The Id of the FileNode.¶

• parentId: "Id|null"¶

  The Id of the parent node, or null if this is a top level node.¶

• nodeType: "String" (immutable; default: server-inferred)¶

  The type of node. Values are registered in the "JMAP FileNode Types" registry (see IANA Considerations). This document defines the following values: "file", "directory", and "symlink". This is immutable after creation. If not provided on creation, the server infers the type: "file" if blobId is non-null, "symlink" if target is non-null, "directory" otherwise. Attempting to change nodeType after creation is an "invalidProperties" error.¶

• blobId: "Id|null"¶

  The blobId for the content of this node. MUST be non-null for file nodes (including zero byte files). MUST be null for directory and symlink nodes. Creating or updating a file node to have a null blobId is an "invalidProperties" error. Updating the blobId replaces the node's content; the server MUST update size to match the new blob. A blob referenced by a FileNode MUST NOT be expired or garbage collected by the server while the FileNode exists.¶

• target: "String[]|null"¶

  The target path for symlink nodes, as an array of path elements. MUST be non-null for symlinks. MUST be null for file and directory nodes. Each element is a node name in the path. An empty string as the first element indicates an absolute path from the root of the tree; otherwise the path is relative to the symlink's parent. An element of ".." refers to the parent directory. The target is not required to resolve to an existing node (symlinks may dangle). The target is mutable — updating it changes where the symlink points.¶

• size: "UnsignedInt|null" (server-set)¶

  The size in bytes of the associated blob data. This MUST be null for directory and symlink nodes, and non-null for file nodes. Size is optional on create and update, but if provided it MUST match the size of the provided blobId. If the client updates blobId without providing size, the server sets size from the new blob and returns the size in the "updated" response.¶

• name: "String"¶

  User-visible name for the FileNode. This MUST be a Net-Unicode string [UNICODE] of at least 1 character in length, subject to the maximum size given in the capability object. There MUST NOT be two sibling FileNodes with both the same parent and the same name. The server MUST reject names containing any character listed in forbiddenNameChars, or matching any entry in forbiddenNodeNames (case-insensitively), with an "invalidProperties" error. See Implementation Considerations for guidance on which characters and names to forbid.¶

• type: "String|null"¶

  The media type of the FileNode. This MUST be null for directory and symlink nodes, and non-null for file nodes. Valid values are found in the IANA media-types registry. Servers MUST NOT reject media types that are not recognised. Servers MUST reject media types if the value does not conform to the ABNF of [MEDIATYPE] Section 4.2.¶

• created: "UTCDate" (default: current server time)¶

  The date the node was created.¶

• modified: "UTCDate|null" (default: current server time)¶

  The date the node was last updated. The server does not automatically update this value. If the client does not include modified in an update, the server MUST leave it unchanged. If the client sets modified to null, the server MUST set it to the current server time. See Implementation Considerations for usage guidance.¶

• accessed: "UTCDate|null" (default: current server time)¶

  The date the node was last accessed. As with modified, the server does not automatically update this value; clients SHOULD provide an updated value when appropriate. If not included in an update, the server MUST leave it unchanged. If set to null, the server MUST set it to the current server time.¶

• changed: "UTCDate" (server-set)¶

  The date the server last recorded a change to any property of this node. The server MUST automatically update this value whenever any property of the node is modified, including blobId, name, parentId, shareWith, executable, and all other mutable properties. This is not settable by clients.¶

• executable: "Boolean" (default: false)¶

  If true, the node should be treated as an executable by operating systems that support this flag.¶

• isSubscribed: "Boolean" (default: true)¶

  This property is stored per user, and if true, the node should be displayed to the current user. Some servers may not allow this field to be changed for some or all nodes, e.g. only for directories, or only for nodes on which the shareWith ACL is actually set for this user, not nodes which inherit their ACL from a parent.¶

• myRights: "FilesRights" (server-set)¶

  The set of rights (ACLs) the user has in relation to this node. A FilesRights object has the following properties:¶

  • mayRead: Boolean The user may read the properties and blob content of this node.¶

  • mayAddChildren: Boolean The user may create child nodes in this directory.¶

  • mayRename: Boolean The user may rename or move this node.¶

  • mayDelete: Boolean The user may destroy this node.¶

  • mayModifyContent: Boolean The user may update the content-related properties of this node (blobId, type, target, modified, accessed, executable).¶

  • mayShare: Boolean The user may change the sharing of this node (see [JMAP-SHARING]).¶

• shareWith: "Id[FilesRights]|null"¶

  A map of userId to rights for users this node is shared with. The owner of the node MUST NOT be in this set. This is null if the user requesting the object does not have myRights.mayShare, or if the node is not shared with anyone.¶

• role: "String|null"¶

  An indication that this directory has a special role. The role MUST be null for files. A node with the "root" role should have a null parentId. Clients MUST ignore unrecognised role values. Values are registered in the "JMAP FileNode Roles" registry (see IANA Considerations).¶

3.2. FileNode Methods

4.1. PUT

A PUT request replaces the entire content of the node. The request body is the new content. The Content-Type header sets the media type of the node.¶

On success, the server MUST update the node's blobId, size, and type properties, and return an HTTP 200 response with a JSON body:¶

{
  "blobId": "Bnewblob123",
  "size": 48576,
  "type": "text/plain"
}

4.2. PATCH

A PATCH request applies a partial modification to the node's current content. The Content-Type of the request indicates the patch format. The supported patch formats are those listed in the supportedPatchTypes capability of [JMAP-BLOBEXT] (e.g., application/x-rdiff-delta, application/x-bsdiff, text/x-diff). The server applies the delta to the node's current blob to produce the new content.¶

On success, the server MUST update the node's blobId and size properties. The type is not changed unless the client includes an X-FileNode-Type header, in which case the server MUST update the node's type to the header value. The response is an HTTP 200 with the same JSON body as PUT:¶

{
  "blobId": "Bpatched456",
  "size": 49152,
  "type": "text/plain"
}

Servers that do not support a given patch format MUST respond with HTTP 415 (Unsupported Media Type).¶

7.1. Examples

To archive an entire directory tree rooted at FileNode "dirabc" into a zip file:¶

json [["Blob/convert", { "accountId": "account1", "create": { "myarchive": { "archive": { "type": "application/zip", "entries": [{ "nodeId": "dirabc", "name": "/", "recurse": true }] } } } }, "R1"]] ¶

To archive specific files from different locations along with a full subdirectory:¶

json [["Blob/convert", { "accountId": "account1", "create": { "selective": { "archive": { "type": "application/zip", "entries": [ { "nodeId": "filenode1", "name": "README.txt" }, { "nodeId": "dirnode2", "name": "docs/", "recurse": true } ] } } } }, "R1"]] ¶

7.2. Extracting Archives into FileNodes

When both capabilities are present, the ExtractRecipe (defined in [JMAP-BLOBEXT]) is extended with the following additional properties:¶

• parentNodeId: "Id|null" A FileNode id of a directory. When present, the server extracts the archive contents into this directory, creating FileNode objects for each entry. Subdirectories in the archive are created as directory FileNodes. File entries become file FileNodes with their blobId set to the extracted content. The created and modified timestamps are taken from the archive entry metadata. If the archive entry includes a mode field, the server SHOULD use it to set the executable property on the created FileNode.¶

• onExists: "String|null" (default: null) Controls the behaviour when an extracted entry would collide with an existing FileNode name under the same parent. The values and semantics are the same as for FileNode/set (see above): null rejects with an alreadyExists SetError, "replace" destroys the existing node, "rename" gives the new node a server-chosen name, and "newest" replaces the existing node only if the archive entry has a strictly later modified timestamp.¶

When parentNodeId is set, each ArchiveEntry in the response entries array includes an additional nodeId property containing the id of the FileNode that was created for that entry.¶

If parentNodeId references a FileNode that does not exist, is not a directory, or for which the user does not have mayAddChildren permission, the server MUST reject the Blob/convert creation with an appropriate SetError (notFound, invalidProperties, or forbidden).¶

8.1. Modification Timestamps

Clients SHOULD provide an updated modified value when modifying a node. This gives clients control over the timestamp, for example when preserving original modification times during file synchronization. Clients that do not care about preserving timestamps can set modified to null to have the server use the current time.¶

Clients may also choose to update the modified timestamp on a parent directory when moving a child node in or out, to reflect that the directory's contents have changed.¶

8.2. Timestamp Precision

The UTCDate type (RFC 3339) supports fractional seconds. Servers SHOULD include sub-second precision in created, modified, accessed, and changed timestamps where their storage backend supports it. Clients MUST preserve fractional seconds when round-tripping timestamps back to the server.¶

8.3. Filename Character Restrictions

Servers should set forbiddenNameChars and forbiddenNodeNames to include characters and names that are problematic for their storage backend and for the broadest set of clients.¶

The following characters are problematic on common platforms:¶

• Windows: <, >, :, ", \, |, ?, *, and control characters (U+0000-U+001F). Windows also forbids trailing dots and spaces in names.¶

• macOS: : (HFS+ legacy; displayed as / in Finder).¶

• Linux: the null byte (U+0000).¶

The following names are problematic:¶

• All platforms: . and .. (path traversal).¶

• Windows: reserved device names CON, PRN, AUX, NUL, COM0-COM9, and LPT0-LPT9. These are reserved regardless of file extension (e.g., "CON.txt" is also forbidden).¶

A server targeting broad client compatibility should include at least /<>:"\|?* in forbiddenNameChars and at least ., .., and the Windows reserved names in forbiddenNodeNames.¶

8.4. Case Sensitivity

Windows and macOS filesystems are typically case-insensitive (treating "Foo" and "foo" as the same name), while Linux filesystems are typically case-sensitive. Clients syncing to case-insensitive platforms should use compareCaseInsensitively on FileNode/set requests to prevent creating sibling nodes whose names differ only in case, as these cannot coexist on the target platform.¶

8.5. Access Time Updates

Updating accessed on every file read generates significant API traffic for little value. Clients are encouraged to use a "relatime" strategy similar to modern POSIX filesystems: only update accessed if the current value is older than modified, or if more than 24 hours have elapsed since the last accessed update. Clients should batch access time updates with their next JMAP request rather than making a dedicated call.¶

9.1. Path Traversal

Clients that reconstruct filesystem paths from FileNode hierarchies MUST validate the resulting paths and reject any that would escape the intended directory tree. Servers SHOULD include / in forbiddenNameChars and . and .. in forbiddenNodeNames to prevent path traversal attacks via node names.¶

9.2. Symlink Targets

Symlink targets are not validated by the server to point to existing nodes. Clients that resolve symlinks MUST guard against symlink loops (a symlink pointing to an ancestor of itself) and MUST NOT follow symlinks outside the FileNode tree. Servers SHOULD impose a limit on the length of target values and MAY reject targets containing ".." path components.¶

9.3. Denial of Service

Deep nesting of FileNodes or very large numbers of children under a single parent can consume significant server resources. Servers SHOULD enforce reasonable limits via maxFileNodeDepth and MAY impose additional limits on the number of children per node. Recursive operations such as destroying a subtree with onDestroyRemoveChildren can be expensive; servers SHOULD impose limits on the size of subtrees that can be destroyed in a single operation.¶

9.4. Access Control

The discoverability rules defined in this document mean that ancestor nodes of shared content are visible (with mayRead false) to users who have access to descendants. While these ancestor nodes do not expose file content, their names and structure may reveal information about the file hierarchy. Server administrators and users sharing content should be aware of this.¶

Changes to the shareWith property on a node affect all descendants. Removing sharing from a parent node will make all descendants undiscoverable to the affected users, which may be surprising if those users had been actively working with the shared files.¶

9.5. Content Security

Servers that perform content scanning or malware detection SHOULD scan blobs referenced by FileNode objects. The type property is client-asserted and MUST NOT be trusted for security decisions; servers SHOULD independently verify content types where this matters.¶

10.1. JMAP Capability registration for "filenode"

IANA is requested to register the "filenode" JMAP Capability as follows:¶

Capability Name: urn:ietf:params:jmap:filenode¶

Specification document: this document¶

Intended use: common¶

Change Controller: IETF¶

Security and privacy considerations: this document, Security Considerations¶

10.2. JMAP Error Codes registration for "nodeHasChildren"

IANA is requested to register the "nodeHasChildren" JMAP Error Code as follows:¶

JMAP Error Code: nodeHasChildren¶

Intended use: common¶

Change Controller: IETF¶

Description: The node being destroyed is still referenced by other nodes which have not been destroyed.¶

Reference: this document¶

10.3. JMAP Data Types registration for "FileNode"

IANA is requested to register the "FileNode" JMAP Data Type as follows:¶

Type Name: FileNode¶

Can Reference Blobs: Yes¶

Can Use For State Change: Yes¶

Capability: urn:ietf:params:jmap:filenode¶

Reference: this document¶

10.4. JMAP FileNode Types Registry

IANA is requested to create a new "JMAP FileNode Types" registry with the following initial values. New registrations are subject to Specification Required ([IANA-GUIDELINES]).¶

10.5. JMAP FileNode Roles Registry

IANA is requested to create a new "JMAP FileNode Roles" registry with the following initial values. New registrations are subject to Expert Review ([IANA-GUIDELINES]).¶

14.1. Normative References

[IANA-GUIDELINES]

Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/rfc/rfc8126>.

[JMAP-BLOBEXT]

Gondwana, B., "JMAP Blob Extensions", Work in Progress, Internet-Draft, draft-gondwana-jmap-blobext-06, 7 April 2026, <https://datatracker.ietf.org/doc/html/draft-gondwana-jmap-blobext-06>.

[JMAP-CORE]

Jenkins, N. and C. Newman, "The JSON Meta Application Protocol (JMAP)", RFC 8620, DOI 10.17487/RFC8620, July 2019, <https://www.rfc-editor.org/rfc/rfc8620>.

[JMAP-SHARING]

Jenkins, N., Ed., "JSON Meta Application Protocol (JMAP) Sharing", RFC 9670, DOI 10.17487/RFC9670, November 2024, <https://www.rfc-editor.org/rfc/rfc9670>.

[MEDIATYPE]

Freed, N., Klensin, J., and T. Hansen, "Media Type Specifications and Registration Procedures", BCP 13, RFC 6838, DOI 10.17487/RFC6838, January 2013, <https://www.rfc-editor.org/rfc/rfc6838>.

[RFC2119]

Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/rfc/rfc2119>.

[RFC8174]

Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

[URI-TEMPLATE]

Gregorio, J., Fielding, R., Hadley, M., Nottingham, M., and D. Orchard, "URI Template", RFC 6570, DOI 10.17487/RFC6570, March 2012, <https://www.rfc-editor.org/rfc/rfc6570>.

14.2. Informative References

[CALDAV]

Daboo, C., Desruisseaux, B., and L. Dusseault, "Calendaring Extensions to WebDAV (CalDAV)", RFC 4791, DOI 10.17487/RFC4791, March 2007, <https://www.rfc-editor.org/rfc/rfc4791>.

[CARDDAV]

Daboo, C., "CardDAV: vCard Extensions to Web Distributed Authoring and Versioning (WebDAV)", RFC 6352, DOI 10.17487/RFC6352, August 2011, <https://www.rfc-editor.org/rfc/rfc6352>.

[JMAP-CALENDARS]

Jenkins, N. and M. Douglass, "JSON Meta Application Protocol (JMAP) for Calendars", Work in Progress, Internet-Draft, draft-ietf-jmap-calendars-26, 4 November 2025, <https://datatracker.ietf.org/doc/html/draft-ietf-jmap-calendars-26>.

[JMAP-CONTACTS]

Jenkins, N., Ed., "JSON Meta Application Protocol (JMAP) for Contacts", RFC 9610, DOI 10.17487/RFC9610, December 2024, <https://www.rfc-editor.org/rfc/rfc9610>.

[JMAP-MAIL]

Jenkins, N. and C. Newman, "The JSON Meta Application Protocol (JMAP) for Mail", RFC 8621, DOI 10.17487/RFC8621, August 2019, <https://www.rfc-editor.org/rfc/rfc8621>.

[JMAP-QUOTAS]

Cordier, R., Ed., "JSON Meta Application Protocol (JMAP) for Quotas", RFC 9425, DOI 10.17487/RFC9425, June 2023, <https://www.rfc-editor.org/rfc/rfc9425>.

[UNICODE]

Klensin, J. and M. Padlipsky, "Unicode Format for Network Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008, <https://www.rfc-editor.org/rfc/rfc5198>.

[WEBDAV]

Dusseault, L., Ed., "HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)", RFC 4918, DOI 10.17487/RFC4918, June 2007, <https://www.rfc-editor.org/rfc/rfc4918>.