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Convert SRT to VTT with the SubtoVTT API

Convert SRT to VTT programmatically with the SubtoVTT API. One POST, one credit, instant WebVTT output. Free API key to test. v1 · stable

Convert SRT to VTT programmatically with one HTTP request. The SRT to VTT API takes your .srt file and returns WebVTT (.vtt) — the native caption format of the HTML5 <video> element and the format most streaming platforms ingest.

SRT and WebVTT share the same cue structure, so timing and text carry over; the API adds the WEBVTT header and converts the timestamp syntax. One credit per conversion, 100 free credits on your first key.

Why convert SRT to VTT with an API

  • Automate: run conversions in CI/CD, ingestion pipelines, or cron jobs.
  • Batch: process whole libraries of .srt files without a desktop app.
  • Integrate: drop conversion into a video platform or captioning workflow.

Convert with cURL

curl -X POST https://api.example.com/api/v1/convert \
  -H "Authorization: Bearer your_api_key" \
  -F "[email protected]" \
  -F "from=srt" \
  -F "to=vtt" \
  -o movie.vtt

Compact example — Python

import os, requests

resp = requests.post(
    "https://api.example.com/api/v1/convert",
    headers={"Authorization": f"Bearer {os.environ['SUBTOVTT_API_KEY']}"},
    files={"file": ("movie.srt", open("movie.srt", "rb"), "application/x-subrip")},
    data={"from": "srt", "to": "vtt"},
)
resp.raise_for_status()
print("Cues:", resp.headers.get("X-Cue-Count"))
open("movie.vtt", "wb").write(resp.content)

Full examples by language

Format notes

Topic Detail
Output WebVTT (.vtt), UTF-8
Header Adds the WEBVTT declaration line
Timestamps Same timing; 00:00:01,000 → 00:00:01.000
Styling Cue settings like align: and position: supported
Usage HTML5 video, most streaming platforms

Note: SRT is plain text with one cue per block, so nothing is lost moving to WebVTT.

FAQ

How much does SRT to VTT conversion cost? One credit per conversion. Keys start with 100 free credits; top-ups are $2/1k, $9/10k, or $40/50k.

Can I adjust timing in the same request? Yes — pass shift_ms to shift timestamps, or use the two-point resync params (two_point_t1, t1p, t2, t2p) for non-linear drift.

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