Merge Videos API — Combine Multiple Videos into One MP4

Combine 2-50 video URLs into a single MP4 with optional crossfade or fade transitions. 1 credit per merge.

New: Combine multiple video clips into a single MP4 with a single API call. Supports hard cuts, crossfade, and fade-to-black transitions. All inputs are automatically normalized to the target resolution.

Pricing

Operation	Credits	Price (Pro Yearly)	Price (Pro Monthly)
Merge (any transition)	1	$0.006	$0.012

Credits are deducted upfront. Refunded automatically if the merge fails.

Endpoint

POST https://vicsee.com/api/v1/tools/merge-videos

See Authentication for API key setup.

Parameters

Parameter	Type	Required	Description
videos	array	Yes	Array of video objects (2-50). Each object has `url` (string, required) and optional `trim` object with `start`/`end` (numbers, seconds).
transition	string	No	`"none"` (default) = hard cut. `"crossfade"` = smooth blend. `"fade"` = fade through black.
transition_duration	number	No	Transition duration in seconds (0.1-5.0). Default: 0.5. Only used when transition is not `"none"`.
resolution	string	No	Output resolution as `WIDTHxHEIGHT`. Default: `"1080x1920"`. All inputs are scaled and padded to fit.

Example Request

curl -X POST https://vicsee.com/api/v1/tools/merge-videos \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "videos": [
      { "url": "https://example.com/scene1.mp4" },
      { "url": "https://example.com/scene2.mp4" },
      { "url": "https://example.com/scene3.mp4" }
    ],
    "transition": "crossfade",
    "transition_duration": 0.5
  }'

Response

{
  "success": true,
  "data": {
    "id": "task_abc123",
    "model": "merge-videos",
    "status": "completed",
    "output": {
      "url": "https://assets.vicsee.com/vicsee/dew/2026-02-28-xyz/merge.mp4",
      "duration": 15.5,
      "videoCount": 3
    },
    "creditsUsed": 1,
    "creditsRemaining": 499,
    "createdAt": "2026-02-28T12:00:00.000Z"
  }
}

The response returns immediately with the merged video URL — no polling needed. The duration field contains the output video duration in seconds.

Trim Example

Trim each clip before merging — useful when you only need a segment of each video:

curl -X POST https://vicsee.com/api/v1/tools/merge-videos \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "videos": [
      { "url": "https://example.com/intro.mp4", "trim": { "end": 3.0 } },
      { "url": "https://example.com/main.mp4", "trim": { "start": 2.0, "end": 10.0 } },
      { "url": "https://example.com/outro.mp4", "trim": { "start": 1.0 } }
    ]
  }'

Transitions

None (default): Hard cut between clips. Fastest processing — no re-encoding overlap between clips.

Crossfade: Smooth blend where the outgoing clip fades out while the incoming clip fades in simultaneously. Best for scenes that flow together.

Fade: Fade through black — the outgoing clip fades to black, then the incoming clip fades in from black. Best for distinct scene changes.

Limits

Constraint	Value
Minimum videos	2
Maximum videos	50
Supported formats	MP4, MOV, WebM
Transition duration	0.1-5.0 seconds
Resolution	Any (default: 1080x1920)

Errors

Code	HTTP	Description
`MISSING_VIDEOS`	400	`videos` array not provided
`TOO_FEW_VIDEOS`	400	Less than 2 videos
`TOO_MANY_VIDEOS`	400	More than 50 videos
`INVALID_VIDEO_URL`	400	Video URL missing or invalid
`INVALID_TRANSITION`	400	Transition not `"none"`, `"crossfade"`, or `"fade"`
`INVALID_TRANSITION_DURATION`	400	Duration not between 0.1 and 5.0
`INSUFFICIENT_CREDITS`	402	Not enough credits
`MERGE_FAILED`	500	FFmpeg merge failed

Merge Audio + Video — Combine a video with a separate audio track
Tasks API — Check task history
Credits API — Check your credit balance

Merge Videos

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