ADD_MASK_KEYFRAMES API Documentation

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Interface Information

POST /openapi/capcut-mate/v1/add_mask_keyframes

Function Description

Add mask keyframes to video segments that already have a mask. Keyframes are written on the segment common_keyframes list and can animate position (X/Y), size (width/height), feather, and rotation. Units match add_masks: pixels for position and size, 0–100 for feather, degrees for rotation.

The segment must already have a mask from add_masks. This API does not create a mask and does not change the mask material's static config.

Request Parameters

{
  "draft_url": "https://capcut-mate.jcaigc.cn/openapi/capcut-mate/v1/get_draft?draft_id=2025092811473036584258",
  "keyframes": [
    {"segment_id": "d62994b4-25fe-422a-a123-87ef05038558", "offset": 0, "X": 0, "Y": 0, "width": 540, "height": 540, "feather": 0, "rotation": 0},
    {"segment_id": "d62994b4-25fe-422a-a123-87ef05038558", "offset": 5000000, "X": -360, "Y": -200, "width": 1076, "height": 1071, "feather": 100, "rotation": 180}
  ]
}

Parameter Description

Parameter	Type	Required	Default	Description
draft_url	string	✅	""	Full URL of the target draft
keyframes	array	✅	[]	Mask keyframe list

keyframes

Field	Type	Required	Description
segment_id	string	✅	Target video segment ID
offset	integer	✅	Time offset from the segment start, in microseconds
X	number	❌	Mask center X in pixels, relative to material center, right is positive
Y	number	❌	Mask center Y in pixels, relative to material center, down is positive
width	number	❌	Mask width in pixels
height	number	❌	Mask height in pixels
feather	number	❌	Feather amount, 0–100
rotation	number	❌	Rotation in degrees

X, Y, width, height, feather, and rotation are optional, but each item must include at least one of them. 0 is a valid value. For position or size animation, send both axes at the same offset. Sending only X writes the X-axis keyframe only; sending only width writes KFTypeMaskSizeX only.

Writing the same property at the same timestamp on the same segment overwrites the previous value.

Response

{
  "code": 0,
  "message": "success",
  "draft_url": "https://capcut-mate.jcaigc.cn/openapi/capcut-mate/v1/get_draft?draft_id=2025092811473036584258",
  "keyframes_added": 12,
  "affected_segments": ["d62994b4-25fe-422a-a123-87ef05038558"]
}

Field	Type	Description
draft_url	string	Draft URL
keyframes_added	integer	Number of draft properties written (X/Y and width/height each count as 1)
affected_segments	array	Segment IDs that received keyframes

Examples

Position keyframes

curl -X POST https://capcut-mate.jcaigc.cn/openapi/capcut-mate/v1/add_mask_keyframes \
  -H "Content-Type: application/json" \
  -d '{
    "draft_url": "YOUR_DRAFT_URL",
    "keyframes": [
      {"segment_id": "segment-id", "offset": 0, "X": 0, "Y": 0},
      {"segment_id": "segment-id", "offset": 5000000, "X": -360, "Y": -200}
    ]
  }'

Size keyframes

curl -X POST https://capcut-mate.jcaigc.cn/openapi/capcut-mate/v1/add_mask_keyframes \
  -H "Content-Type: application/json" \
  -d '{
    "draft_url": "YOUR_DRAFT_URL",
    "keyframes": [
      {"segment_id": "segment-id", "offset": 0, "width": 540, "height": 540},
      {"segment_id": "segment-id", "offset": 5000000, "width": 1076, "height": 1071}
    ]
  }'

Feather and rotation

curl -X POST https://capcut-mate.jcaigc.cn/openapi/capcut-mate/v1/add_mask_keyframes \
  -H "Content-Type: application/json" \
  -d '{
    "draft_url": "YOUR_DRAFT_URL",
    "keyframes": [
      {"segment_id": "segment-id", "offset": 0, "feather": 0, "rotation": 0},
      {"segment_id": "segment-id", "offset": 5000000, "feather": 100, "rotation": 180}
    ]
  }'

Error Codes

Code	Message	Description	Solution
2001	Invalid draft URL	Draft missing or not in cache	Check draft_url
2015	Segment not found	segment_id does not exist	Confirm the segment ID
2016	Invalid segment type	Not a video segment	Call this API only on video/image segments
2046	Invalid mask keyframe information	Missing property, invalid feather, or bad format	Check keyframes
2047	No mask found on the segment	The segment has no mask yet	Call add_masks first
2048	Mask keyframe addition failed	Failed to save the draft	Retry or contact support

Notes

• Call Add Masks before adding mask keyframes.
• Position conversion uses the material size (pixels / half material dimension), not the canvas size.
• Size conversion uses the material size (width / material_width, height / material_height), matching the static mask config.
• An offset beyond the segment duration is clamped to the end of the segment.
• Round-corner keyframes are not supported.

Related Interfaces

• Add Masks
• Add Keyframes
• Save Draft

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📚 Project Resources
GitHub: https://github.com/Hommy-master/capcut-mate
Gitee: https://gitee.com/taohongmin-gitee/capcut-mate