6 best AI video extenders: inputs, limits and costs

The key question is “Will this tool accept my source video?” Some extenders accept uploads; others only continue videos generated in their own system. A video expander adds picture around the edges. It does not necessarily make the clip longer.

Magic Hour publishes this guide and includes its own product in the comparison. Treat the recommendations as editorial guidance from a vendor, and verify the linked first-party product details and your own output requirements before choosing a tool.

Best AI Video Extenders at a Glance

Basis: primary product documentation checked September 10, 2026. This is a comparison of supported workflows, not a timed test or a quality ranking. A platform’s newest generation model does not automatically support the extension features of an older one.

1. Magic Hour: a No-Account Trial for Uploaded Footage

Upload a video, let the guest tool generate its continuation, then inspect and download the result. The free flow is automatic: three extensions per day, five seconds each, with a 200 MB upload limit. It is suitable for testing whether a short continuation fixes your ending before choosing a paid workflow.

The signed-in extender offers optional prompt and audio inputs to guide action or pacing. Check the current generation settings and quote for that route. Paid Magic Hour plans include commercial use and watermark-free video exports.

Watch for: identity changes, altered product details and an obvious join. Do not assume a free attempt will be usable just because the job completes. The free extension tutorial shows the upload, queue and download workflow.

2. Adobe Premiere: Short Handles Within an Edit

Generative Extend creates additional material at a clip edge directly in Premiere. Its two-second video limit suits a late cut, transition or reaction that needs a little room. It is not intended to turn a short shot into a long scene.

Adobe supports source resolutions from 360p through 4K in the documented landscape and portrait ratios. Sources can be 12–60 fps, but extensions above 30 fps are generated at 30 fps. Generated sections are 8-bit SDR even when the source has greater bit depth or HDR.

Audio is a separate constraint: eligible mono or stereo audio can extend up to ten seconds. The feature cannot generate spoken dialogue, mutes dialogue during extension and excludes clips containing music. Check the Generative Extend FAQ and the credit cost for your settings.

3. Midjourney: Continue an Existing Image Animation

Midjourney’s video workflow begins with an image and produces a five-second video. Extend adds four seconds at a time, up to four times: 5 → 9 → 13 → 17 → 21 seconds. You can continue automatically or edit the extension prompt.

This is convenient when your B-roll already starts in Midjourney. Its documentation also offers batch sizes of one, two or four videos. Generating fewer candidates per request can reduce unnecessary output when you only need one continuation, though it does not guarantee a lower cost per keeper.

Watch for: GPU-time use, the plan’s SD/HD access and drift after repeated extensions. This feature does not establish support for uploading any finished phone or camera video and extending it directly. An external starting image is different from an external source video.

4. Kling: Auto or Prompt-Guided Continuation

Kling’s Extend with Prompts guide documents continuation after video generation. Auto-Extend adds what the model predicts next; Customized Extend lets you describe the next movement. The guide describes four- to five-second additions and repeated extensions up to three minutes total.

Use the Extend control on an eligible generation. That older guide does not prove that every current Kling model or arbitrary uploaded MP4 supports the same workflow.

Watch for: a prompt that introduces a new subject or setting can cause a cut. Ask for a continuation of the action already visible, such as a person lowering a hand after a wave. A documented maximum duration is not a promise of an uninterrupted, consistent three-minute take.

5. Veo 3.1: API Extension for Veo-Generated Clips

Google’s Gemini API documentation supports extension with Veo 3.1 and Veo 3.1 Fast, but not Veo 3.1 Lite. It requires a video from a previous Veo generation, not arbitrary uploaded footage.

Each extension adds seven seconds at 720p, in 16:9 or 9:16. The input can be up to 141 seconds, with a combined result up to 148 seconds. The guide allows up to 20 extensions and requires the source video to have been generated or referenced within the last two days.

This is an API workflow with separate billing. Google’s current rate table lists 720p video with audio at $0.40 per second for Standard and $0.10 for Fast; it offers no free API tier for these models. Confirm the billable generation details for your request. Listen to the join as well as watching it: native audio does not make every extended line or sound seamless.

6. Pollo AI: Extend a Pollo Generation

Pollo’s extender page tells users to select a video generated with Pollo AI, optionally enter a continuation prompt, then download the extended result. It specifically describes extending Pollo-created videos, including realistic or anime styles.

That makes it relevant if you already have an eligible Pollo asset. The page does not establish one fixed duration or credit price for every model, and it should not be treated as proof that any external upload can be extended.

Watch for: the selected model’s extension option, duration, charge and export terms. Pollo says commercial use requires a premium subscription. A generic “free AI video extender” headline does not define an unlimited free generation allowance.

What About Runway, Luma and Pika?

Runway: older lists recommend Gen-3 Alpha Extend. Runway’s current help article says Gen-3 Alpha retired July 8, 2026 and Gen-3 Alpha Turbo retired July 30. Its replacements include Gen-4.5, Animate Frames and Edit Studio Aleph 2.0. Do not buy a subscription expecting that retired Extend workflow.

Luma: its Ray2 guide documents an Extend function for that model. Its Reframe feature solves a different problem: changing the visible canvas. Verify the exact model and current extension control; neither the older Ray2 guide nor a Ray3.2 Reframe demo establishes identical limits for all Luma workflows.

Pika: creating a transition between still frames or generating a longer clip is not automatically the same as extending uploaded video. Confirm that the selected tool accepts your source and adds time after it, rather than returning a new animation. Our video-extension workflow guide explains the last-frame workaround when a direct extender is unavailable.

Choose the Cheapest Edit That Solves the Problem

Before buying more generations, check whether you need new motion at all.

For an example budget, suppose six B-roll shots each need a five-second tail. Two attempts per shot means 12 attempts and 60 generated seconds, even though the edit uses at most 30 added seconds. Price the attempts using the actual tool quote, then divide total spend by approved clips. Include any subscription purchase, cleanup and sound work. This is a planning example, not a measured success rate.

Stop extending once the edit has enough material. An unused ten-second tail still consumes time or credits, and a longer generation creates more frames to inspect.

A Useful Same-Clip Comparison

Use one clear source shot and specify the smallest continuation you need. Where a platform only supports its own outputs, label that as a different-input comparison rather than pretending the test is identical.

1. Watch the join at normal speed. A visible pause or jump can matter more than a beautiful final frame.
2. Inspect identity and objects. Check faces, hands, clothing, logos and held products.
3. Check the camera and light. Look for an abrupt change in framing, direction, exposure or shadows.
4. Listen through the transition. Check speech, ambience, music and any silent gap.
5. Inspect the downloaded file. Confirm duration, dimensions, frame rate and watermark status.
6. Record all attempts. Compare the cost of footage you can use, not only the price of a successful generation request.

These are suggested acceptance checks, not tests we claim to have run. Keep the original clip so a bad continuation never becomes the only available version.