# Auto subtitles

- Human page: https://happytails.ai/en/subtitle-tools/auto-subtitles/
- Markdown: https://happytails.ai/en/subtitle-tools/auto-subtitles.md
- Structured JSON: https://happytails.ai/agents/en/subtitle-tools/auto-subtitles/index.json
- Visibility: public

## Tool capabilities

| Property | Value |
| --- | --- |
| Tool ID | `auto-subtitles` |
| Category | subtitle-tools |
| Implementation | Registered implementation. Registration alone is not a production-quality guarantee. |
| Browser execution | Use the visible action or interactive controls. |
| Browser processing | Server required |
| HTTP API | /api/v1/tools/auto-subtitles/run |
| Browser-agent interface | run_current_tool |

### Implementation notes

Runs with local model weights on this website’s server. No external AI API is used. Review the result for errors. Local Whisper tiny. Clips up to five minutes; review words and timing.

### Inputs and settings

No free-text input is required. Use the file inputs and/or settings below.

Accepted browser files: `.wav,.mp3,.m4a,.flac,.mp4,.mov,.webm`. Choose one file.

Browser file-input limit: 20971520 bytes in total. HTTP limits can differ.

No additional settings are declared for this tool.

### HTTP contract

API calls process supplied data on the server. The website origin is `https://happytails.ai`. Server API hosting is not connected on the public website yet. Use your local server origin to test these requests.

```http
POST https://happytails.ai/api/v1/tools/auto-subtitles/run
Content-Type: application/json
```

[Detailed operation reference](https://happytails.ai/en/api/tools/auto-subtitles.md) · [Shared API guide](https://happytails.ai/en/api.md)

#### Limits

| Limit | Value |
| --- | --- |
| request_bytes | 31457280 |
| input_characters | 1000000 |
| files_bytes | 20971520 |
| max_files | 1 |
| timeout_seconds | 90 |

#### Complete input schema

```json
{
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "input": {
      "type": "string",
      "maxLength": 1000000,
      "default": "",
      "description": "Plain text input. File tools use files instead unless otherwise documented."
    },
    "options": {
      "type": "object",
      "additionalProperties": false,
      "properties": {}
    },
    "files": {
      "type": "array",
      "maxItems": 1,
      "items": {
        "type": "object",
        "required": [
          "name",
          "base64"
        ],
        "additionalProperties": false,
        "properties": {
          "name": {
            "type": "string",
            "maxLength": 200,
            "description": "Filename only, no path."
          },
          "mime": {
            "type": "string",
            "maxLength": 150
          },
          "bytes": {
            "type": "integer",
            "minimum": 0,
            "description": "Optional decoded byte count; must match content if supplied."
          },
          "base64": {
            "type": "string",
            "contentEncoding": "base64",
            "description": "File bytes as padded base64. Use the tool-specific limits.files_bytes value for the total decoded input size."
          }
        }
      }
    }
  }
}
```

#### Complete output schema

```json
{
  "type": "object",
  "required": [
    "tool",
    "result"
  ],
  "properties": {
    "tool": {
      "type": "string"
    },
    "result": {
      "type": "object",
      "required": [
        "text",
        "files"
      ],
      "properties": {
        "text": {
          "type": [
            "string",
            "null"
          ]
        },
        "data": {
          "description": "Parsed JSON when the textual result is JSON."
        },
        "name": {
          "type": "string"
        },
        "mime": {
          "type": "string"
        },
        "files": {
          "type": "array",
          "items": {
            "type": "object",
            "required": [
              "name",
              "mime",
              "bytes",
              "base64"
            ],
            "properties": {
              "name": {
                "type": "string"
              },
              "mime": {
                "type": "string"
              },
              "bytes": {
                "type": "integer"
              },
              "base64": {
                "type": "string",
                "contentEncoding": "base64"
              }
            }
          }
        }
      }
    }
  }
}
```

#### Error and retry handling

Failures return a non-200 status and `error.code` plus `error.message`. Correct invalid input before retrying; retry server-busy responses with bounded backoff. Returned files contain Base64 data, not persistent download URLs. Decode and inspect the output before treating conversion as successful. See the shared API guide for the complete status and timeout rules.

### Browser-agent workflow

1. Open the human page in a browser that supports WebMCP.
2. Discover the interface exposed by that page; use its actual schema.
3. Select files on the page first when the tool requires files.
4. Call `run_current_tool` with valid input and settings.
5. Inspect the returned result or error and the displayed output. Retrieve files from the displayed download links.

Calls do not automatically copy or download results. Browser permissions still apply. Interface availability alone is not proof of successful execution.

### Planning specification

Generate timed captions from audio or video; edit in playback view; enforce readable line lengths; export SRT and VTT from one canonical generator.

This describes intended requirements. Use the implementation notes, interface schema and observed output to determine current support.

### Complete machine-readable capability record

```json
{
  "id": "auto-subtitles",
  "category": "subtitle-tools",
  "built": true,
  "requirements": "Generate timed captions from audio or video; edit in playback view; enforce readable line lengths; export SRT and VTT from one canonical generator.",
  "implementation": {
    "fields": [],
    "files": true,
    "accept": ".wav,.mp3,.m4a,.flac,.mp4,.mov,.webm",
    "multiple": false,
    "input": false,
    "processing": "Server required",
    "native": true,
    "ai": true,
    "maxFileBytes": 20971520,
    "note": "Runs with local model weights on this website’s server. No external AI API is used. Review the result for errors. Local Whisper tiny. Clips up to five minutes; review words and timing.",
    "experience": {
      "automatic": false,
      "single": false,
      "label": "Your text",
      "placeholder": "Type or paste your input…",
      "help": "Up to 1,000,000 characters. Review the settings before running.",
      "action": null
    },
    "mode": "explicit",
    "interactive": false
  },
  "execution": "POST /api/v1/tools/auto-subtitles/run",
  "api": {
    "id": "auto-subtitles",
    "name": "Auto subtitles",
    "category": "subtitle-tools",
    "description": "Generate draft SRT captions from recorded speech.",
    "notes": "Runs with local model weights on this website’s server. No external AI API is used. Review the result for errors. Local Whisper tiny. Clips up to five minutes; review words and timing.",
    "human_path": "/en/subtitle-tools/auto-subtitles/",
    "method": "POST",
    "endpoint": "/api/v1/tools/auto-subtitles/run",
    "schema_url": "/api/v1/tools/auto-subtitles",
    "input_schema": {
      "type": "object",
      "additionalProperties": false,
      "properties": {
        "input": {
          "type": "string",
          "maxLength": 1000000,
          "default": "",
          "description": "Plain text input. File tools use files instead unless otherwise documented."
        },
        "options": {
          "type": "object",
          "additionalProperties": false,
          "properties": {}
        },
        "files": {
          "type": "array",
          "maxItems": 1,
          "items": {
            "type": "object",
            "required": [
              "name",
              "base64"
            ],
            "additionalProperties": false,
            "properties": {
              "name": {
                "type": "string",
                "maxLength": 200,
                "description": "Filename only, no path."
              },
              "mime": {
                "type": "string",
                "maxLength": 150
              },
              "bytes": {
                "type": "integer",
                "minimum": 0,
                "description": "Optional decoded byte count; must match content if supplied."
              },
              "base64": {
                "type": "string",
                "contentEncoding": "base64",
                "description": "File bytes as padded base64. Use the tool-specific limits.files_bytes value for the total decoded input size."
              }
            }
          }
        }
      }
    },
    "output_schema": {
      "type": "object",
      "required": [
        "tool",
        "result"
      ],
      "properties": {
        "tool": {
          "type": "string"
        },
        "result": {
          "type": "object",
          "required": [
            "text",
            "files"
          ],
          "properties": {
            "text": {
              "type": [
                "string",
                "null"
              ]
            },
            "data": {
              "description": "Parsed JSON when the textual result is JSON."
            },
            "name": {
              "type": "string"
            },
            "mime": {
              "type": "string"
            },
            "files": {
              "type": "array",
              "items": {
                "type": "object",
                "required": [
                  "name",
                  "mime",
                  "bytes",
                  "base64"
                ],
                "properties": {
                  "name": {
                    "type": "string"
                  },
                  "mime": {
                    "type": "string"
                  },
                  "bytes": {
                    "type": "integer"
                  },
                  "base64": {
                    "type": "string",
                    "contentEncoding": "base64"
                  }
                }
              }
            }
          }
        }
      }
    },
    "processing": "Server; self-hosted native engine, no external conversion service",
    "limits": {
      "request_bytes": 31457280,
      "input_characters": 1000000,
      "files_bytes": 20971520,
      "max_files": 1,
      "timeout_seconds": 90
    }
  },
  "agent_processing": "Server; self-hosted native engine, no external conversion service",
  "browser_agent": {
    "supported": true,
    "name": "run_current_tool",
    "discovery": "WebMCP on the human page in a supporting browser",
    "verification": "See audit/API-AUDIT.md; availability is not verification"
  }
}
```

## Page guide

Generate draft SRT captions from recorded speech.

## Useful next steps

- [Subtitle editor](https://happytails.ai/en/subtitle-tools/subtitle-editor/): Cue text/timing editing, validation and export without automatic transcription. ([Markdown](https://happytails.ai/en/subtitle-tools/subtitle-editor.md))

- [Subtitle translator](https://happytails.ai/en/subtitle-tools/subtitle-translator/): Translate subtitle text while preserving cue timing. ([Markdown](https://happytails.ai/en/subtitle-tools/subtitle-translator.md))

- [SRT to VTT](https://happytails.ai/en/subtitle-tools/srt-to-vtt/): Convert timestamp punctuation and cue structure. ([Markdown](https://happytails.ai/en/subtitle-tools/srt-to-vtt.md))

## How to use Auto subtitles

1. Choose a file in WAV, MP3, M4A, FLAC, MP4, MOV or WEBM.
2. Review the settings, then choose Run Auto subtitles.
3. Review the result, then use Copy result or a download link when available.

## What to expect

Generate draft SRT captions from recorded speech. Runs with local model weights on this website’s server. No external AI API is used. Review the result for errors. Local Whisper tiny. Clips up to five minutes; review words and timing.