At Line 21, we work across a wide spectrum of live content. Captions are an integral part of how you reach, respect, and engage your audience.

When it comes to live captioning, how those captions are displayed is usually the first step, and most technical process for our clients. We try to take the cross-eyed out of constructing a solid captioning experience.

Below, we explore four common display paths for live captions. We offer context, comparisons, and candid guidance to help content producers, accessibility managers, and technical leads make informed choices.

1. Traditional Browser

What is it?

A simple web page that displays live captions as streaming text, often refreshed in real time. There is no video present on this page. Typically used alongside a separate audio or video stream.

What does it look like?

A plain browser window showing live text as it is transcribed. Viewers follow the dialogue or spoken content by reading the live captions. The format is usually accessible, mobile-friendly, and readable across devices.

Pros

• Works on virtually any device with a browser
• No dependency on video player compatibility
• Very low bandwidth requirements
• Accessible for users who only need text, such as Deaf or hard-of-hearing participants

Limitations

• Captions are separate from the video or audio experience
• Requires the viewer to manage two windows or devices to follow both content and captions
• No support for syncing with visuals or speaker indicators unless manually styled

Who it serves best

Audiences who need clear, direct access to live caption text, especially in low-bandwidth or accessibility-first settings.

This is also regularly used for 'on-site captions' where a second LED screen will be positioned to the side of the stage. Think lyrics at Coachella, or a keynote speaker at an expo.

2. Subtitle Overlay (Open Captions or Burned-In)

What is it?

Captions rendered as an overlay on top of content, whether that content is a video, a webinar, or another real-time interaction. If used by event production, these captions will be burned into the feed, and the audience will not be able to turn them off.

If the overlay is being used by an individual on their own device, this is a floating, malleable text overlay that can be less disruptive than having a separate browser open.

What does it look like?

Text is permanently visible on the video, in the location you place the overlay on screen. This is typically at the bottom. Styling is fixed at the source and cannot be modified by the viewer.

Pros

• Universally visible on all devices and platforms
• No dependency on player support for captions
• Ensures compliance where togglable captions are not guaranteed

Limitations

• Cannot be turned off by the viewer
• Styling is locked in - no user customisation (and this does matter)
• One language only unless multiple languages are stacked, which can be cluttered

Who it serves best

For live events, this is a tool best used when presenting visual information that would use a 'banner-style' for text at the bottom. Much like a news broadcast, or corporate stakeholder update.

We've even seen art exhibits project a subtitle overlay onto a wall during a panel - it really is a flexible tool for the right events.

3. HLS Video Players (Timed Text Tracks)

What is it?

The 'newest' on the block for better video accessibility, and curated engagement for audiences.

Captions delivered via HLS (HTTP Live Streaming) as separate timed text tracks, commonly using WebVTT. These are referenced in the master playlist and displayed in players that support them.

What does it look like?

Viewers can either visit a video player embedded into the event production website, or visit a standalone page hosted by Line 21. Unlike other providers, we include the end-to-end process, saving you the need to subscribe to yet another third-party video solution.

Viewers have a CC (closed caption) toggle in the video player, allowing them to choose their language and caption style.

Pros

• Supports multiple languages
• Efficient for scalable live streaming workflows
• Integrated with modern streaming ecosystems and CDNs

Limitations

• Variable support across devices and platforms
• Needs proper setup in the stream manifest
• Styling and behavior can differ depending on player implementation

Who it serves best

If you don't want a hefty Vimeo subscription, and like many of us, want to curate your audience engagement, then this is the popular solution. You can customise your viewer page, video player studio, and be accessible in real-time, without being locked behind older tech and higher pricing.

You have the advantage over CEA-608 of including more languages, with less delay, and better accuracy.

Audiences can watch on their own devices, and feel confident they have an accessible route for captions if they need them. And your budget won't creak from video streaming giants putting accurate third-party captions on a paywall.

4. RTMP with Embedded CEA-608/708

What is it?

Captions embedded in the video stream using broadcast standards like CEA-608 or CEA-708. Used in RTMP workflows where the captions are injected at source and travel in-band.

Who it serves best

Audiences watching through broadcast systems or legacy solutions. And when we say legacy, include destinations such as Vimeo, Twitch, YouTube, Facebook, and TikTok.

Giants are slow to adopt HLS solutions, and so audiences are hostage to older technology with built-in delays in the stream. Some of these platforms will only allow third party captions if you have an enterprise account, effectively putting a price tag on accurate accessibility for audiences.

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Choosing the right method for displaying live captions can feel daunting, especially when balancing accessibility, technical requirements, and audience experience. If you're a first-timer, the learning curve is steep.

Even with limited resources, there are effective and scalable captioning options available. Understanding your technical boundaries, and being open to creative workflows can unlock high-impact results without high costs.

At Line 21, we help demystify these decisions and ensure your captions show up exactly where and how they're needed.