Themes

A theme is a custom CSS stylesheet stored under a short code, and anyone holding the code can fetch it. The HTTP API exposes one operation, which stores a theme. The Media Proxy serves the stored stylesheet back through Get theme CSS.

The single route here is user-only. A bot token and an OAuth2 bearer credential are both rejected with 403 ACCESS_DENIED.

Theme identifier

A theme identifier is 16 lowercase hexadecimal characters matching ^[a-f0-9]{16}$. Fluxer draws eight cryptographically random bytes for each request and renders them as hex, so storing identical CSS twice produces two independent themes under two independent identifiers.

Example

{
  "id": "3f0a91c7d2b84e65"
}

Document bounds

The UTF-8 encoding of a submitted document cannot exceed 8388608 bytes, and the document is at least one character long. Both bounds are fixed constants of the instance.

Bound	Value
Encoded CSS1 2	8388608 bytes
Submitted CSS3	at least 1 character

¹ The 8 MiB ceiling is inclusive, so a document whose UTF-8 encoding is exactly 8388608 bytes is stored and one byte more is rejected with 400 FILE_SIZE_TOO_LARGE

² Measured over the UTF-8 encoding, so a document of multi-byte characters can be shorter than 8388608 characters and still be rejected

³ Measured in characters of the submitted string

An account holds no theme quota. The route bucket is the only bound on how many themes an account creates, and no route here consults an instance limit key.

Content screening

The instance-wide content filter screens the submitted document before the route runs. It checks a css value of at least 3 characters against the instance phrase blocklist and the instance URL blocklist. A match on either returns 403 CONTENT_BLOCKED. A shorter value is never screened.

Fluxer scans a body under every content type except multipart/form-data and application/x-www-form-urlencoded. A body that does not parse as JSON is skipped as well. The route parses the body from the raw request text and reads no content type, so a JSON document sent under either form content type is stored without passing the blocklists.

The screen precedes the rate limit bucket, the credential check, and the request schema, so a blocked document returns CONTENT_BLOCKED even when the request has no credential.

The screen is the only inspection the document receives. Fluxer stores the CSS verbatim and never parses, validates, minifies, or rewrites it.

Create theme

POST/v1/users/@me/themes

Stores a custom CSS document and returns 201 with the created theme identifier. User-only, and no permission is required.

JSON body

Field	Type	Description
css1 2	string	The CSS text to store and share (at least 1 character)

¹ Stored verbatim, bounded by the 8388608-byte UTF-8 ceiling described in Document bounds

² An empty string is rejected with the validation code INVALID_FORMAT

Malformed and unusable bodies fail at different paths

An absent body, a whitespace-only body, and a present but empty, null, or non-string css all return 400 INVALID_FORM_BODY with INVALID_FORMAT at the css path. A body that does not parse as JSON returns the same status and code at the body path.

A body that parses as JSON but is not an object, such as a string, a number, an array, or null, returns the same code at the path root.

Response body

Field	Type	Description
id	string	The theme identifier

The object has the identifier and nothing else.

Response

Status	Body	Condition
201	response body	Document was stored
400	error response	The encoded document exceeds the size ceiling and the request returns FILE_SIZE_TOO_LARGE
403	error response	Caller is a bot or presents a bearer credential and the request returns ACCESS_DENIED
403	error response	The account has an outstanding required action and the request returns ACCOUNT_SUSPICIOUS_ACTIVITY
403	error response	The document is blocked by content moderation and the request returns CONTENT_BLOCKED

Side effects

Fluxer stores the UTF-8 encoding of the submitted document with the content type text/css; charset=utf-8. The identifier addresses the document by the time the caller receives it.

Nothing Fluxer stores links a theme to the account that created it. The Media Proxy then serves the stored document from /themes/{id}.css, and that route accepts no credential.

Theme CSS is public and permanent

The identifier is the only thing guarding a stored document, and the read route is unauthenticated. The HTTP API replaces or deletes no stored theme. A caller MUST NOT put a credential, a token, or any other secret in a submitted document.

Rate limit

20 requests per minute for each authenticated user, on the theme:share:create bucket.