# Free tools API (https://voicelabs.now/docs/free-tools-api) The free tools on voicelabs.now also answer over HTTP, with **no API key and no account**. They are separate from the [Developer API](/api): that one is keyed and part of VoiceLabs Pro; these are small utilities anyone can call from a script, a CI job or an AI agent. The OpenAPI 3.1 document for them is at [`https://voicelabs.now/api/tools/openapi.json`](https://voicelabs.now/api/tools/openapi.json). Every operation in it has `security: []` and the tag `Free tools`. ## The contract [#the-contract] * **No authentication.** Nothing is read from cookies or headers to identify you, so CORS is `*`. * **POST** a JSON body, a form, or `multipart/form-data` with the file in the `file` field. * **GET** takes the same fields as query parameters, for small inputs. * **JSON by default.** Send `Accept: text/markdown` to get the result as a Markdown document instead, or `download=1` to get the resulting file itself with a `Content-Disposition: attachment` header. * **Errors are [RFC 9457](https://www.rfc-editor.org/rfc/rfc9457) problem documents** (`application/problem+json`) with `title`, `status` and a `detail` written for a person. * **Rate limit: 30 calls a minute and 300 a day per address.** Past either, the answer is `429` with a `Retry-After` header. * Every response carries `X-Tool-Docs: https://voicelabs.now/docs/free-tools-api`. * Inputs are processed in memory and not stored. ## Convert SRT to VTT (or VTT to SRT) [#convert-srt-to-vtt-or-vtt-to-srt] `POST https://voicelabs.now/api/tools/srt-to-vtt` — the API behind [the SRT to VTT converter](https://voicelabs.now/tools/srt-to-vtt). | Field | Required | Meaning | | ------------------- | -------- | ----------------------------------------------------------------------------------------------------- | | `input` (or `file`) | yes | The whole `.srt` or `.vtt` file. The format is detected from the content. Up to 2,000,000 characters. | | `to` | no | `vtt` or `srt`. Default: the other format. | | `download` | no | `1` to get the file instead of JSON. | ```sh curl -s https://voicelabs.now/api/tools/srt-to-vtt -F file=@subtitles.srt -F download=1 -o subtitles.vtt ``` The JSON answer is `{ "output", "format", "cueCount", "warnings" }`. `warnings` lists everything the target format cannot hold and that was therefore removed: SRT `` and `{\an8}` tags going to WebVTT; voice, class, language and ruby tags, cue settings and NOTE/STYLE/REGION blocks going to SRT. ``, `` and `` are kept both ways, and every time is copied to the millisecond. ## Shift subtitle timing [#shift-subtitle-timing] `POST https://voicelabs.now/api/tools/subtitle-timing-shift` — the API behind [the subtitle timing shift tool](https://voicelabs.now/tools/subtitle-timing-shift). | Field | Required | Meaning | | ------------------- | -------- | ------------------------------------------------------------------------------------------------------------------- | | `input` (or `file`) | yes | The whole `.srt` or `.vtt` file. The result keeps its format. | | `offset_seconds` | yes | Seconds to move every cue: positive is later, negative earlier. Millisecond precision, at most 24 hours either way. | | `from_seconds` | no | Shift only the cues that start at or after this time. Default `0`. | | `download` | no | `1` to get the file instead of JSON. | ```sh curl -s https://voicelabs.now/api/tools/subtitle-timing-shift \ -H 'Content-Type: application/json' \ -d '{"input":"1\n00:00:05,000 --> 00:00:07,000\nHello","offset_seconds":-1.5}' ``` A cue that would end before `00:00:00` is removed and one that would start before it starts at `00:00:00`; both are counted in `warnings`. WebVTT inline timestamps (`<00:00:01.000>`) move with their cue. ## Validate SSML [#validate-ssml] `POST https://voicelabs.now/api/tools/ssml-validator` — the API behind [the SSML validator](https://voicelabs.now/tools/ssml-validator). | Field | Required | Meaning | | ------------------------------ | -------- | -------------------------------------------- | | `ssml` (or `input`, or `file`) | yes | The SSML document. Up to 200,000 characters. | ```sh curl -s https://voicelabs.now/api/tools/ssml-validator \ -H 'Accept: text/markdown' \ --data-urlencode 'ssml=Hello world' ``` The JSON answer is `{ "valid", "errors", "warnings", "elementCount", "textCharacters" }`; each error and warning has a `line`, a `column` and a `message`. An invalid document is still a `200` with `valid: false`. Errors are what XML or the [W3C SSML 1.1 Recommendation](https://www.w3.org/TR/speech-synthesis11/) forbids: an unclosed or mismatched tag, an element in a place it is not allowed, a missing required attribute, or a value outside its grammar (such as `time="5"` on ``). Vendor extensions such as `` or ``, and a `` without `version`, `xml:lang` or `xmlns`, are warnings: most engines accept them. ## Errors [#errors] | Status | When | | ------ | -------------------------------------------------------------------------------------------------------------- | | `400` | A required field is missing or not a number (`offset_seconds`), or `to` is not `srt`/`vtt`. | | `413` | The body is over 2.5 MB. | | `415` | The body is not JSON, a form or multipart. | | `422` | The input has no subtitle cues in it, the shift would leave none, or the SSML document is over the size limit. | | `429` | Over 30 calls a minute or 300 a day from one address. |