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A join job stitches an ordered list of video clips into a single output file. Each clip can be a static video URL or a nested job definition that renders first. The whole pipeline - render child jobs, wait for them, stitch - is handled in one API call.

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How It Works

Submit a POST /jobs/join request with an ordered assets array. Each asset is either:
  • type: "video" - a direct URL to an existing video file
  • type: "job" - a job definition that Nexrender renders first, then uses the output
When job assets are present, Nexrender renders all child jobs in parallel, waits for them to complete, then stitches the outputs in the order you specified.

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Basic Example - Static Videos

The simplest case: stitch two existing video files together. 
curl -X POST https://api.nexrender.com/api/v2/jobs/join \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "assets": [
      {
        "type": "video",
        "src": "https://cdn.example.com/intro.mp4"
      },
      {
        "type": "video",
        "src": "https://cdn.example.com/outro.mp4"
      }
    ]
  }'

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Mixed Example - Render and Stitch

Render a personalized middle segment from a template and stitch it between a static intro and outro. 
curl -X POST https://api.nexrender.com/api/v2/jobs/join \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "assets": [
      {
        "type": "video",
        "src": "https://cdn.example.com/intro.mp4"
      },
      {
        "type": "job",
        "template": {
          "id": "PERSONALIZED_TEMPLATE_ID",
          "composition": "main"
        },
        "assets": [
          {
            "type": "text",
            "layerName": "name",
            "value": "Sarah Chen"
          },
          {
            "type": "image",
            "layerName": "avatar",
            "src": "https://cdn.example.com/users/sarah.jpg"
          }
        ]
      },
      {
        "type": "video",
        "src": "https://cdn.example.com/outro.mp4"
      }
    ],
    "settings": {
      "preset": "mp4"
    },
    "webhook": {
      "url": "https://yourdomain.com/webhooks/stitch-complete"
    }
  }'
The parent enters pending while the child job renders. Once the child finishes, the stitch runs automatically and the parent transitions to finished.

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Request Fields

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Top-level

FieldTypeRequiredDescription
assetsarrayYesOrdered list of clips to stitch (minimum 1)
settings.presetstringNoOutput format - currently "mp4"
uploadobjectNoPush output to your S3-compatible bucket (same schema as regular jobs)
webhookobjectNoCallback URL for status notifications

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Video Asset (type: "video")

FieldTypeRequiredDescription
typestringYesMust be "video"
srcstringYesURL to the video file

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Job Asset (type: "job")

FieldTypeRequiredDescription
typestringYesMust be "job"
template.idstringYesTemplate ID for the child job
template.compositionstringYesComposition to render
assetsarrayNoAssets to inject into the child job
previewbooleanNoRender child at preview quality
settings.qualitystringNo"draft" or "full"
settings.codecstringNoOutput codec
settings.enginestringNoAE engine version: "ae2025" or "ae2026"

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Tracking a Join Job

Track the join job with GET /jobs/:id as you would any other job. When all child jobs are rendering, the parent is pending. Once children complete and the stitch begins, the parent moves to render:dorender, then finished. The outputUrl in the creation response is populated immediately and points to where the final stitched file will be available once the job is finished.

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When to Use Join Jobs

Join jobs are the right choice when you want to concatenate clips end-to-end:
  • Intro + personalized body + outro for marketing emails or event invites
  • Chapter-by-chapter assembly of a long-form video from separate renders
  • Combining a rendered animation with pre-recorded footage clips
If you need to composite one render as a layer inside another composition (rather than appending clips), use a Nested Job instead.

Nested Jobs

Composite child renders as layers inside a parent composition

Batch Jobs

Submit up to 1,000 jobs in a single request