How Much Delay Does Real-Time AI Dubbing Have? Data From 2,700+ Real Dubs (2026)

Two different delays

"Delay" in real-time AI dubbing can mean two things, and a single number can hide which one it is:

• Start delay: how long after you press the button the first dubbed sentence plays. It's a wait while the dub loads, and it doesn't affect the video after that.
• Lag behind the speaker: once the dub is running, how far each dubbed sentence falls behind the person speaking. This is the one you notice while watching, and it depends on how the tool works.

How long EarDub takes to start

Half of all dubs on YouTube start within about 11 seconds of the click, and on course sites within about 8 seconds.

How we measured it

• The clock: the time between two events from the same viewer, the click on Dub and the first dubbed audio. Both are recorded when they reach our server, so network time affects them slightly.
• Who's counted: real viewers on the versions of EarDub in use that week. Our own test account is excluded.
• What's excluded: clicks with no audio within 5 minutes, for example when a viewer stopped the dub, wasn't signed in, reached a plan limit or hit an error.
• What's mixed in: first-time dubs and videos someone has already dubbed, captioned videos and videos without captions, fast and slow connections, and any YouTube ad that plays before the video. We didn't remove these, because viewers see them too.

Why the first sentence takes a few seconds

Before the first word plays, EarDub has to get the video's captions or recognize its speech, build whole sentences, translate them with the context of the video and generate the voice. After that it keeps preparing sentences ahead of where you're watching. If you jump to a new point, the first sentence there takes a few seconds to prepare, and then it's ahead again.

Does the voice lag behind the speaker?

It depends on where the tool gets the words from:

• Tools that listen as the video plays can only translate a sentence after hearing it, so the voice trails the speaker. In exchange, they can work on live streams.
• Tools that prepare ahead, like EarDub, work from captions or from audio the player has already loaded, so a sentence can be ready before the speaker reaches it and start at the same moment. They can't dub live streams.

In our own testing, once the dub is playing, EarDub's voice matches the speaker or trails by less than a sentence, so it stays in real-time sync. If a translated sentence runs longer than the original, EarDub speeds the speech up by at most 1.45x rather than cutting it off, so the voice keeps pace instead of falling further behind.

How to test any dubbing extension yourself

1. Pick a 10–15 minute video with a fast speaker. Use the same video, computer and network for every tool, with only one dubbing extension on at a time.
2. Skip past any ad, then press the tool's dub button and time how long the first dubbed sentence takes.
3. Keep the original audio quietly audible and watch for sentences that start late, get cut off or go missing.
4. Jump ahead a few minutes and time how long the dub takes to come back.
5. Repeat on a video nobody has dubbed recently, since a repeat run can be faster when a tool reuses earlier work.

Which tool should you use?

For recorded videos, a dub that's prepared ahead gets you a voice that can start with the speaker, for a wait of a few seconds at the beginning. That's the approach EarDub takes, on YouTube, Udemy, Coursera and most other sites, free for 30 minutes a day. For a live stream, use a live-audio tool and accept the lag.