If you're evaluating Synthesia alternatives, the short answer is: HeyGen Avatar V on HiAPI generates the same category of output — a lip-synced digital-human video driven by a script or by audio you already have — but as a metered API call instead of a seat-licensed web app. No editor login, no monthly minimum, and pricing that scales with the seconds of video you actually render. Real output samples are below.
Why look for a Synthesia alternative
Synthesia earned its reputation on fast corporate training and explainer videos made through a hosted editor. Teams that outgrow that workflow usually aren't unhappy with the avatar quality — they're running into how the product is packaged. A seat-based subscription is sized for a content team clicking through a UI, not for a backend job that needs to render avatar video on a schedule or on demand. If you're trying to wire avatar generation into an app, CMS, or automation pipeline rather than having someone manually export a file, the constraint is the access model, not necessarily the avatar engine itself. That's the specific gap HeyGen Avatar V on HiAPI is built to fill.
What HeyGen Avatar V actually does
HeyGen Avatar V takes either a typed script plus a voice preset, or a driving audio file, and returns a lip-synced avatar video:
- Script-driven — pass
prompt(up to 5,000 characters) andvoice; the API generates narration and syncs the avatar's mouth to it. - Audio-driven — pass
audio_urlinstead, and the avatar lip-syncs directly to audio you already produced (up to 600 seconds, 32 MiB). - Output controls —
resolution(720p/1080p/4k),aspect_ratio(six options including9:16for vertical),output_format(mp4/webm), plusfit,remove_background, and abackgroundoverride. - Captions — set
caption: trueand the finished task returns an SRT file alongside the video. - Pricing — a flat $0.15 per second of output video, with no resolution surcharge. A 30-second clip is $4.50 regardless of whether it's rendered at 720p or 4K.
- Access — a single
POST https://api.hiapi.ai/v1/taskscall; poll the task or use a callback to retrieve the finishedoutput[]array.
Real output: two takes from the model
Long-form narrator, 1080p
Heres the pricing breakdown you asked for, explained simply.
Rendered with avatar: "Brandon Business Standing Front" and voice: "Jack Sterling" at resolution: "1080p". Worth noting honestly: a background color override (#0F172A) was requested for this clip but didn't take effect — the avatar kept its native filmed office backdrop instead. If a specific background matters for your use case, test it before committing to a production run.
Short-form vertical, with captions
New drop just landed, swipe up and shop now!
Rendered with avatar: "Riley Casual Front" and voice: "Cute Chloe" at aspect_ratio: "9:16" and caption: true, which also returned a sidecar SRT file for this clip. This is the same short-form vertical avatar workflow we cover in more depth for social/ad placements.
Synthesia vs. HeyGen Avatar V: the real difference is the access model
The two products land in the same category — script-to-avatar-video — but they're packaged for different consumers:
| Synthesia | HeyGen Avatar V on HiAPI | |
|---|---|---|
| Access | Hosted web editor, seat-based plans | Direct API, POST /v1/tasks |
| Pricing unit | Subscription tier / bundled credits | $0.15 per second rendered |
| Best fit | A person building videos by hand in a UI | A pipeline or app generating video programmatically |
| Output | Lip-synced avatar video | Lip-synced avatar video (script or audio-driven) |
If your workflow is "a person logs in and exports a file," a UI-first tool like Synthesia is a reasonable fit. If your workflow is "a service needs to generate avatar video as part of a larger pipeline," a usage-based API is the better shape — and that's the gap HeyGen Avatar V is built for, using the same task-based pattern as every other video model on HiAPI.
FAQ
Does HeyGen Avatar V support captions?
Yes. Set caption: true and a successful task returns both the video (type: "video") and an SRT file (type: "caption") in the output array.
What's the maximum video length?
Audio-driven generation supports up to 600 seconds of driving audio (32 MiB max). Script-driven length depends on the script — prompt accepts up to 5,000 characters.
Which resolutions and aspect ratios are available?
720p, 1080p, and 4k, with six aspect ratios: 16:9, 9:16, 4:5, 5:4, 1:1, and auto.
Is pricing really flat regardless of resolution?
Yes — the only pricing factor is estimated_seconds, at $0.15/second. Resolution doesn't change the cost.
Can I drive the avatar with existing audio instead of a script?
Yes — pass audio_url instead of prompt/voice and the avatar lip-syncs directly to that audio.
Get started
Full parameter reference, avatar presets, and voice presets are on the HeyGen Avatar V model page. For the request/response shape shared across every video model on HiAPI, see the Unified Async API quickstart — the same POST /v1/tasks → poll/callback → output[] pattern shown above.
