AI subtitle generator

A subtitle editor built for precision

Automatic generation gets you most of the way; the subtitle editor is how you close the last stretch quickly, and it is why production teams use Sonix instead of fixing auto-captions inside a video platform.

Smart splitting you control

Sonix splits your transcript into cues based on limits you choose: characters per line, one or two lines, and cue duration. Adjust the limits and the page re-splits instantly, so you can go from YouTube-friendly cues to broadcast-length cues without retyping anything. If a break lands mid-thought, split the cue where you want it; to join short cues, raise the limits and let the transcript re-split.

Timing anchored to the words themselves

Every cue is anchored to the word-level timestamps captured during transcription. Each cue's in and out points come from when its first and last words are actually spoken, not from dividing the runtime into equal chunks. That is why cues land on natural phrase boundaries, and why changing your splitting rules never drifts the subtitles out of sync. The timing survives every re-split.

A visual timeline with draggable cues

Every cue appears on a visual timeline against your media. Drag a cue's edges to change its start and end points, or click any word to hear the audio at that exact moment and confirm the timing by ear. You get frame-accurate control without learning a dedicated captioning application.

Millisecond timecode control

Adjust any cue down to the millisecond. If you trim your video or change its speed after generating subtitles, shift every cue at once instead of fixing them one at a time. Fast dialogue and overlapping speakers stay in sync because timing is anchored to word-level timestamps, not sentence averages.

Edit the words, keep the timing

The subtitle text is fully editable. Fix a name, correct a technical term or tighten phrasing, and the cue keeps its timing. Find-and-replace pairs apply across the whole transcript, so a misspelled name is corrected in every cue at once, and speaker identification carries through so you know who said what while you edit.

This is the practical difference between a subtitle maker and a text box on a video timeline: you edit subtitles as structured, timed data, and the file stays valid in every export format.

Style captions, then burn them in

Subtitle files like SRT and VTT leave appearance up to the player; when captions need to look a specific way everywhere, Sonix styles them and embeds them permanently in the video.

Full styling control

Customize the font, text color, size, background and position of your subtitles. Preview changes in real time before you export, so what you approve is exactly what viewers see. Match your brand guidelines or bump the contrast and size for readability.

Burn-in captions for social media

Burn-in, also called hardcoded subtitles, renders your styled captions directly into the video file. Viewers cannot turn them off, which is exactly what you want on Instagram, TikTok and LinkedIn, where most people watch with sound off and platform caption support varies. Pick the canvas for the destination, including the 9:16 story frame, and Sonix renders the burned-in video for you and delivers a ready-to-share file, no video editor required.

The burned-in video downloads as an MP4 with H.264 video and AAC audio, ready to upload directly to Instagram, TikTok, LinkedIn and YouTube. The canvas you pick sets the frame, and the captions are drawn at the output size, so the text stays crisp.

When to burn in and when to export a file

Burn in for social clips and anywhere you cannot upload a sidecar file. Export SRT or VTT when the platform supports toggleable captions and you want viewers to control them. Sonix produces both from the same transcript, so you never redo the timing work.

Which subtitle file to export

One transcript, every deliverable: Sonix works as an SRT file generator, a VTT generator and a post-production exporter from the same project, with correct timecodes and character encoding in each file.

A VTT file for a web player

Export WebVTT from the same project with one click: the same cues and timing, formatted for HTML5 video.

An SRT file, fast

Upload your video, review the cues and download the .srt file. That is the entire answer to how to create an SRT file: no timecode math and no hand-formatting.

Premiere Pro and Final Cut Pro

Export FCPXML for Final Cut Pro, or bring the SRT into Premiere Pro. Sonix also connects directly to Adobe Premiere Pro, so your subtitle work travels into the edit instead of being redone there.

Broadcast delivery

TTML export supports broadcast and streaming workflows, and Sonix subtitles meet FCC captioning requirements and international broadcast standards when properly reviewed.

For upload steps by file type, see the guides to adding subtitles to MP4, MOV and AVI files.

Translate subtitles, keep the timing

Your subtitle timing is an asset, and Sonix lets you reuse it in every language you publish in.

After transcribing, translate your transcript into any of 54+ languages with one click. Every translation keeps the original subtitle timing, so your Spanish, French, German, Japanese or Chinese captions stay synced to the exact moments already perfected in the editor. Export a separate SRT or VTT file for each language from one upload.

Review happens in a side-by-side editor that shows the original transcript next to the translation, synced to your audio. Edit either side, and the subtitle timing holds. Teams that need native-speaker review use the AI translation as a first draft and polish it in place.

This is how one interview becomes a subtitle set for a global audience without re-timing a single cue. Explore automated translation and the full list of supported languages.

Generate subtitles at scale with the Sonix API

Everything on this page is also available through the API, so high-volume teams can add subtitles to video automatically and never open the editor.

The Sonix REST API lets you upload media, run transcription and retrieve finished subtitle files. Request transcript.srt or transcript.vtt for any media file, with the same splitting controls the editor offers: limit cues by characters or duration, set maximum characters per subtitle, set maximum cue duration, and choose one or two lines per cue.

Webhooks notify your system when files finish processing, and direct integrations with Zapier, Dropbox, Google Drive and Box handle file movement. A media library, a course platform or a newsroom can pipe every published video through the same subtitle standards. See the API documentation for endpoints and parameters.

What the best AI subtitle generators share

If you are comparing subtitle tools, five capabilities decide how much time you actually save.

Word-level timing, not sentence-level

Tools that timestamp whole sentences produce captions that lag or lead the speaker. Sonix timestamps every word to within 100 milliseconds, so cues track the audio even through fast dialogue.

A real editor

Auto-generation is table stakes. The work is in the review, so the editor matters most: a visual timeline, audio playback on click, millisecond control and instant re-splitting of cues.

Every export your workflow needs

One project should produce SRT for YouTube, VTT for the web, TTML for broadcast, FCPXML for the edit bay and a burned-in video for social. Redoing timing per format is the hidden cost of lightweight tools.

Translation that preserves timing

Multilingual publishing should reuse your timing work, not repeat it. A translated SRT should be minutes away from the original, with every cue where it was.

Ownership

YouTube's auto-captions are view-only and stay on YouTube. With Sonix you own the caption files and can use them anywhere: social, broadcast, streaming platforms or your own site.

The rest of the subtitle workflow

This page covers the generator itself, the engine, the editor and the exports; two related pages cover what comes next.

For platform workflows, including how to get your finished files into YouTube, Premiere Pro and TikTok, and how the major formats compare, see our complete guide to automated subtitles and captions.

Sonix also generates SDH subtitles with speaker identification and sound descriptions for deaf and hard-of-hearing viewers, for content that has to meet accessibility requirements.

And if you are starting from a specific file on your desktop right now, the walkthrough on how to add subtitles to films in minutes takes you from the file to a finished subtitle track.