Closed Caption Generator

Create, edit and export SRT and VTT captions with WCAG compliance checking, reading speed analysis and video preview. Free, private and no sign-up.

What is a free closed caption generator online?

A free closed caption generator online is a tool that creates time-coded text files — usually in SRT or WebVTT format — that display the spoken words and relevant sound effects of a video as on-screen text. Captions are called "closed" because viewers can turn them on or off, unlike "open" captions that are permanently burned into the video pixels.

This closed caption generator online is an editor-first tool. Instead of uploading a video for automatic speech recognition, it gives you a full caption authoring environment: add cues, type or paste text, set precise start and end times, add speaker labels and sound-effect notation, and validate everything against WCAG 2.1 and industry captioning standards before you export.

How to use this free closed caption generator

1. Click + Add cue to start building your caption track, or paste a transcript into Auto-split from text to generate cues automatically.
2. Enter a start time and end time for each cue. The editor accepts formats like 00:00:01.500, 1:30 or 90 (seconds).
3. Type the caption text. Add a speaker name if you want a Speaker: prefix (SRT) or a <v Speaker> voice span (VTT).
4. Check the issues panel for WCAG compliance warnings: reading speed, line length, cue duration, overlapping cues and more.
5. Load an existing SRT or VTT file in the Import tab to edit an existing caption file.
6. Use the Video Preview tab to load a video from your device and see your captions overlaid as the video plays.
7. Download SRT or VTT, or copy the file content to your clipboard.

Closed captions vs subtitles: what's the difference?

The terms are often used interchangeably, but they describe different things. Subtitles translate spoken dialogue into another language, assuming the viewer can hear the original audio. Closed captions transcribe all significant audio — dialogue, speaker identification, sound effects, music, tone and meaningful non-speech sounds — and are designed for viewers who are deaf or hard of hearing.

Both use the same file formats (SRT and VTT) and both can be added to any modern video player. The main difference is content: a subtitle track contains only the words; a caption track contains the words plus everything a deaf viewer needs to fully understand the video.

What are the WCAG caption requirements?

The Web Content Accessibility Guidelines (WCAG) 2.1 define caption requirements for video content. The key success criteria are:

• SC 1.2.2 — Captions (Prerecorded): Captions are provided for all prerecorded audio content in synchronized media. This is a Level A requirement — the minimum.
• SC 1.2.4 — Captions (Live): Captions are provided for all live audio content in synchronized media. This is Level AA.
• SC 1.2.5 — Audio Description (Prerecorded): An audio description is provided for all prerecorded video content. Level AA.

WCAG does not prescribe specific technical limits like line length or reading speed — those come from best-practice guidance published by the BBC, Netflix, and the Described and Captioned Media Program. This tool applies those recommendations so your captions are not just compliant, but genuinely usable.

Best-practice captioning rules this tool checks

• Reading speed (CPS). Characters per second should not exceed 20. Most professional captions stay at 15–17 CPS. This tool flags every cue that exceeds 20 CPS.
• Line length. Maximum 42 characters per line, with a maximum of two lines per cue. Longer lines are harder to scan, especially on mobile.
• Duration. Minimum 1 second and maximum 8 seconds per cue. Very short cues flash on screen and very long cues force viewers to re-read.
• Overlapping cues. Two captions should never display at the same time — the player shows one at a time, so overlapping time ranges cause confusion.
• Sound effects notation. Non-speech sounds should be written in square brackets or parentheses, e.g. [door slams], (music swells).
• Speaker identification. When two or more speakers alternate, prefix the caption with the speaker's name, e.g. Alice: Where were you?.

SRT vs VTT: which format should you use?

SRT (SubRip Subtitle) is the oldest and most widely supported caption format. Every major video player, editing suite and social platform accepts it. It is minimal: only cue number, time range and text. Timestamps use a comma before the milliseconds (00:00:01,000).

VTT (Web Video Text Tracks, WebVTT) is the W3C standard for the web. It starts with the text WEBVTT and supports features SRT does not: styling with CSS, cue identifiers, voice spans (<v Speaker>), text positioning, and HTML-like markup. Timestamps use a period before the milliseconds (00:00:01.000).

Rule of thumb: use SRT when you need maximum compatibility (YouTube, VLC, most editing software). Use VTT when you are publishing to a website, need custom styling, or want to use a native HTML5 <track> element.

Why captions matter for SEO and reach

Captions are not just an accessibility requirement — they improve performance. Search engines cannot watch video, but they can index the text of a caption file. Adding captions lets your video rank for every keyword spoken in it, not just the title and description.

Captions also increase engagement. Approximately 85% of Facebook video is watched without sound, and captioned videos average 12% more views and 40% more engagement. For social media creators, captions are the difference between a viewer who keeps watching and one who scrolls past.

Frequently asked questions