> This page is for Build.

> Append .md to any page URL for clean Markdown. Index: https://docs.speechify.ai/llms.txt.
>
> Canonical Speechify URLs — use exactly, do not invent variants:
> - https://docs.speechify.ai — this site (API reference, SDKs, quickstarts)
> - https://speechify.ai — marketing + product site
> - https://platform.speechify.ai — customer dashboard, signup, API keys, billing
> - https://api.speechify.ai — API base URL
> - https://github.com/Speechify-AI: GitHub org for the API (cookbook, demos, CLI). `github.com/speechify` does not exist.
> - https://status.speechify.ai — status + incidents
> - https://speechify.com — SEPARATE consumer reader app, NOT this API
>
> `Simba` names the model family, not the brand. Model ids: `simba-3.2` (English, recommended) and `simba-3.0` (English, German, Spanish, French, Italian and Portuguese; the default). `simba-english` and `simba-multilingual` are retired: a new workspace that sends either gets `400 model_retired`. `SimbaVoice` / `simbavoice.ai` are retired.
>
> Ask, don't scrape. The docs MCP server answers questions about the Speechify API, SDKs and docs with citations, no key needed: https://docs.speechify.ai/_mcp/server (Streamable HTTP, tool `searchDocs`). Setup: https://docs.speechify.ai/build/guides/get-started/connect-mcp

# Detect Watermark

POST https://api.speechify.ai/v1/audio/watermark/detect
Content-Type: multipart/form-data

Check whether a clip carries the watermark Speechify seals into audio it
generates. Upload the audio as `audio`; nothing about it is stored, and
no voice is read or written.

Read the answer carefully in one direction. A `watermarked: true` is
positive evidence that the audio came from Speechify synthesis. A
`watermarked: false` is NOT proof that it did not: only models
redeployed since the watermark shipped mark their output, the detector
needs at least three seconds of clear speech to judge, and re-encoding
or changing the speed of a clip degrades the mark. Treat a negative as
the absence of evidence rather than as evidence of absence.

Checks are rate-limited well below the synthesis budget: this is a
forensic question, not a data-plane call.

Reference: https://docs.speechify.ai/build/api-reference/v1/audio/watermark/detect

## Authentication

- `Authorization` header (bearer token, required) — Enter your API key with the `Bearer` prefix, e.g. 'Bearer sk_...'.

## Request

### Body (multipart/form-data)

This endpoint expects a multipart form containing a file.

- `audio` (file, required) — The clip to check, at most 25MB. Give the detector at least three seconds of clear speech; below that its confidence is not worth acting on, and below half a second it always reports zero.

## Response

### 200

The clip was checked.

- `watermarked` (boolean, required) — Whether the clip carries the watermark, i.e. whether `confidence` cleared the service's configured bar.
- `confidence` (double, required) — The detector's score for this clip, in [0, 1]. Comparable only between checks made against the same detector version.

## Errors

### 400 Bad Request Error

The request was malformed or failed validation. The response body is the standard `Error` envelope; for validation failures `error.fields` enumerates the offending fields as a `path -> message` map (code = `validation_failed`).

- `error` (ErrorDetail, required)
- `request_id` (string, optional) — Server-side request identifier. Echoes the `Speechify-Request-Id` response header. Stable across the request's lifetime, written to structured logs, and useful when reporting issues.

### 401 Unauthorized Error

Authentication is missing or invalid. The request did not carry a recognised credential (console session token, API key, or worker JWT).

- `error` (ErrorDetail, required)
- `request_id` (string, optional) — Server-side request identifier. Echoes the `Speechify-Request-Id` response header. Stable across the request's lifetime, written to structured logs, and useful when reporting issues.

### 403 Forbidden Error

The credential authenticated, but is not authorised for this resource - typically a workspace-role gate (owner / admin required) or a cross-tenant access attempt.

- `error` (ErrorDetail, required)
- `request_id` (string, optional) — Server-side request identifier. Echoes the `Speechify-Request-Id` response header. Stable across the request's lifetime, written to structured logs, and useful when reporting issues.

### 413 Content Too Large Error

Request body exceeded a per-endpoint size limit (e.g. the file upload cap, KB document upload cap, batch-call CSV cap).

- `error` (ErrorDetail, required)
- `request_id` (string, optional) — Server-side request identifier. Echoes the `Speechify-Request-Id` response header. Stable across the request's lifetime, written to structured logs, and useful when reporting issues.

### 422 Unprocessable Entity Error

The request was well-formed but semantically rejected - typically a referential integrity violation (e.g. flow node references an audio asset in another workspace) or a state machine refusal.

- `error` (ErrorDetail, required)
- `request_id` (string, optional) — Server-side request identifier. Echoes the `Speechify-Request-Id` response header. Stable across the request's lifetime, written to structured logs, and useful when reporting issues.

### 429 Too Many Requests Error

Rate limit or concurrency limit exceeded. `error.code` says which ceiling, and they need different responses: `rate_limited` is the request-rate budget (slow down), `concurrency_limit_reached` is a workspace-wide concurrency ceiling (fewer at once, or raise it), and `conversation_turn_in_progress` is contention over one named conversation (keep one message in flight on it). Every 429 carries `Retry-After` and the request-rate budget headers; the active-call cap also carries `RateLimit-Remaining-Calls: 0`.

- `error` (ErrorDetail, required)
- `request_id` (string, optional) — Server-side request identifier. Echoes the `Speechify-Request-Id` response header. Stable across the request's lifetime, written to structured logs, and useful when reporting issues.

### 500 Internal Server Error

An unexpected server-side error occurred. Safe to retry with exponential backoff for idempotent requests.

- `error` (ErrorDetail, required)
- `request_id` (string, optional) — Server-side request identifier. Echoes the `Speechify-Request-Id` response header. Stable across the request's lifetime, written to structured logs, and useful when reporting issues.

### 502 Bad Gateway Error

An upstream dependency (the TTS composer or voice-metadata service) returned a 5xx. The raw upstream detail is not forwarded - the cause is in the server log; the response is a fixed `upstream_failure` envelope. Safe to retry.

- `error` (ErrorDetail, required)
- `request_id` (string, optional) — Server-side request identifier. Echoes the `Speechify-Request-Id` response header. Stable across the request's lifetime, written to structured logs, and useful when reporting issues.

## Types

### ErrorDetail

- `code` (enum, required) — Stable machine-readable error code. Additive only: codes are never renamed, only deprecated. SDKs may map each code to a typed exception class. Status-code semantics: 4xx codes describe caller-fixable issues; 5xx codes describe server-side failures and are safe to retry with backoff for idempotent requests.
  - Allowed values: `endpoint_moved`, `bad_request`, `validation_failed`, `unauthorized`, `payment_required`, `forbidden`, `not_found`, `method_not_allowed`, `conflict`, `idempotency_conflict`, `payload_too_large`, `unsupported_media_type`, `rate_limited`, `concurrency_limit_reached`, `invalid_api_version`, `internal_error`, `upstream_failure`, `service_unavailable`, `caller_not_found`, `contact_not_found`, `contact_identifier_not_found`, `contact_identifier_conflict`, `contact_resolver_not_found`, `credential_not_found`, `credential_in_use`, `agent_not_found`, `agent_in_use`, `agent_run_not_found`, `kb_not_found`, `kb_document_not_found`, `kb_folder_not_found`, `tool_not_found`, `tool_name_taken`, `channel_instance_not_found`, `team_not_found`, `trigger_not_found`, `store_not_found`, `store_document_not_found`, `hosted_api_not_found`, `api_route_not_found`, `consumer_key_not_found`, `skill_not_found`, `skill_version_not_found`, `file_not_found`, `file_path_taken`, `file_storage_limit_reached`, `store_limit_reached`, `store_document_limit_reached`, `store_bytes_limit_reached`, `store_not_configured`, `store_document_version_conflict`, `store_document_deleted`, `entitlement_override_exists`, `hosted_apis_not_in_plan`, `skills_not_in_plan`, `voice_agents_not_in_plan`, `skill_in_use`, `skill_tool_name_conflict`, `skill_limit_reached`, `agent_skill_limit_reached`, `hosted_api_slug_taken`, `api_route_conflict`, `mount_plan_changed`, `route_output_unavailable`, `route_run_timeout`, `route_run_failed`, `route_run_limit_reached`, `route_read_limit_reached`, `route_write_limit_reached`, `hosted_api_public_refused`, `route_tool_not_readable`, `route_tool_unavailable`, `route_upstream_rate_limited`, `route_upstream_error`, `hosted_mcp_not_enabled`, `hosted_api_busy`, `conversation_not_found`, `phone_number_not_found`, `sip_trunk_not_found`, `voice_not_found`, `audio_asset_not_found`, `builtin_not_found`, `batch_not_found`, `agent_test_not_found`, `workspace_not_found`, `invite_not_found`, `project_not_found`, `cross_project_reference`, `project_has_scoped_credentials`, `project_not_empty`, `project_limit_reached`, `agent_limit_reached`, `project_too_large_to_promote`, `call_not_found`, `message_not_found`, `thread_not_found`, `call_not_active`, `relay_displaces_agent`, `brain_not_found`, `brain_in_use`, `custom_model_not_found`, `custom_model_in_use`, `insufficient_scope`, `purchased_numbers_not_included`, `phone_number_quota_reached`, `batch_calls_not_included`, `voice_cloning_not_included`, `voice_cloning_unavailable_in_region`, `consent_challenge_not_found`, `consent_challenge_expired`, `consent_challenge_already_used`, `consent_phrase_mismatch`, `consent_speaker_mismatch`, `consent_recording_unusable`, `consent_verification_unavailable`, `consent_verification_required`, `watermark_audio_unusable`, `watermark_detection_unavailable`, `workspace_last_owner`, `workspace_last_workspace`, `account_deletion_blocked`, `workspace_free_limit`, `workspace_single_owner`, `invite_email_mismatch`, `invite_already_pending`, `service_account_limit_reached`, `service_accounts_not_in_plan`, `speech_marks_unsupported`, `model_retired`, `too_many_voices`, `content_policy_violation`, `safety_identifier_blocked`, `topup_not_in_plan`, `credit_purchase_unpaid`, `credit_purchase_payment_in_progress`, `tool_config_shared`, `spend_cap_exceeded`, `spend_budget_exceeded`, `project_spend_limit_exceeded`, `project_archived`, `project_not_archived`, `project_not_purged`, `project_restore_window_expired`, `project_name_taken`, `funded_balance_required`, `agent_publish_gate_failed`, `agent_publish_gate_required`, `agent_publish_gate_unavailable`, `agent_publish_gate_tool_unreachable`, `text_channel_not_in_plan`, `channel_not_in_plan`, `text_turn_failed`, `conversation_turn_in_progress`, `conversation_closed`, `conversation_not_reachable`, `conversation_channel_bound`, `conversation_prompt_not_found`, `text_message_quota_exceeded`, `durable_runs_not_in_plan`, `tool_transport_unsupported`, `agent_config_too_large`, `agent_run_not_pending`, `agent_run_action_stale`, `share_link_not_found`, `share_link_exhausted`, `share_link_limit_reached`, `destination_not_allowed`, `international_dialing_not_enabled`, `number_not_sms_capable`, `verification_required`, `intended_use_required`
- `message` (string, required) — Human-readable explanation of this specific occurrence. Safe to surface in UI banners or pass to support. The wording can change between releases; clients should match on `code`, not on the message string.
- `fields` (map from string to string, optional) — Per-field validation errors as `path -> message`. Only present on 400 responses caused by request validation (typically code=`validation_failed`). Keys are field paths in dotted/bracket notation; values are short human explanations safe to inline-surface next to the offending form field.
- `details` (map from string to any, optional) — Structured, endpoint-specific context beyond the flat `fields` map. Present only on the few errors that carry it (e.g. the `used_by` referrer list on a credential delete-conflict); its shape depends on the error `code`. Clients that don't recognise a `details` shape can ignore it - the `code` + `message` contract is unchanged.
- `docs_url` (string, optional) — Link to the documentation that resolves this class of error, when a stable page exists. Rate and concurrency 429s link the API limits reference, which lists each plan's limits and how to raise them.

## Examples

**Request**

```json
{
  "audio": "<file: [object Object]>"
}
```

**Response**

```json
{
  "watermarked": true,
  "confidence": 0.98
}
```