`upload_file`

Attach a file to a file input (selector). Give exactly one source:


MCP tool	`upload_file`
HTTP	`POST /browser/upload`

text, for anything you wrote (JSON, CSV, markdown), with a filename;
file, any file this workspace has, by its uri from workspace://files — a screenshot, a download or a file in Files — without its bytes passing through you;
content, base64, for other binary.

The page reads the type from the filename's extension, so name it report.csv, not report; without one, mime_type picks it.

Parameters

Name	Type	Required	Default
`selector`	Selector	no	—
`text`	string	no	—
`filename`	string	no	—
`mime_type`	string	no	—
`content`	string	no	—
`url`	string	no	—
`wait_timeout`	integer	no	`30`
`file`	string	no	—

Every call names its workspace: an X-Workspace header, or ?workspace=<name>. Sending both is refused. See Workspaces.

Field	Type	Notes
`filename`	string	The name the page sees for the attached file.
`bytes`	integer	Size of the file that was sent.
`url`	string	Current URL after the action.
`title`	string	Page title after the action.
`site_data`	object	Present only when site data was restored, skipped or forgotten in this call.
`page`	object	Present only when this browser was opened with capture=true and the page reported a failure while the call ran: what it caused, and where to read it.

Status	Means
`400`	The request cannot succeed as sent — a missing field, a value that was rejected, or a locator that matched nothing before the wait ran out. Do not retry it unchanged.
`401`	Missing or wrong bearer token.
`404`	No such browser session. It ended, the Grid reaped it, or the id was never real. Open a new one and retry.
`413`	The body is over its cap: 1 MiB of JSON, 64 MiB of upload, 1 MiB of flow YAML. Send less; retrying it unchanged will fail again.
`500`	Something failed that this server did not expect.
`503`	The Grid could not serve this — unreachable, or no free slot for a new browser. Worth retrying after a wait.

Over MCP the same failures arrive as a tool error.

MCP

upload_file()

HTTP

curl -X POST $SELENIUM_FLOW/browser/upload \
  -H "Authorization: Bearer $TOKEN" \
  -H "X-Workspace: $WORKSPACE"