Optimize documents

Usage example

{
  "steps": {
    "optimized": {
      "robot": "/document/optimize",
      "use": ":original",
      "preset": "ebook"
    }
  }
}

Parameters

• output_meta

  Record<string, boolean> | boolean | Array<string>

  Allows you to specify a set of metadata that is more expensive on CPU power to calculate, and thus is disabled by default to keep your Assemblies processing fast.

  For images, you can add "has_transparency": true in this object to extract if the image contains transparent parts and "dominant_colors": true to extract an array of hexadecimal color codes from the image.

  For videos, you can add the "colorspace: true" parameter to extract the colorspace of the output video.

  For audio, you can add "mean_volume": true to get a single value representing the mean average volume of the audio file.

  You can also set this to false to skip metadata extraction and speed up transcoding.

• result

  boolean (default: false)

  Whether the results of this Step should be present in the Assembly Status JSON

• queue

  batch

  Setting the queue to 'batch', manually downgrades the priority of jobs for this step to avoid consuming Priority job slots for jobs that don't need zero queue waiting times

• force_accept

  boolean (default: false)

  Force a Robot to accept a file type it would have ignored.

  By default, Robots ignore files they are not familiar with. 🤖/video/encode, for example, will happily ignore input images.

  With the force_accept parameter set to true, you can force Robots to accept all files thrown at them. This will typically lead to errors and should only be used for debugging or combatting edge cases.

• ignore_errors

  boolean | Array<meta | execute> (default: [])

  Ignore errors during specific phases of processing.

  Setting this to ["meta"] will cause the Robot to ignore errors during metadata extraction.

  Setting this to ["execute"] will cause the Robot to ignore errors during the main execution phase.

  Setting this to true is equivalent to ["meta", "execute"] and will ignore errors in both phases.

• use

  string | Array<string> | Array<object> | object

  Specifies which Step(s) to use as input.

  • You can pick any names for Steps except ":original" (reserved for user uploads handled by Transloadit)
  • You can provide several Steps as input with arrays:
    

    {
      "use": [
        ":original",
        "encoded",
        "resized"
      ]
    }
    

  Tip

  That's likely all you need to know about use, but you can view Advanced use cases.

• preset

  screen | ebook | printer | prepress (default: "ebook")

  The quality preset to use for optimization. Each preset provides a different balance between file size and quality:

  • screen - Lowest quality, smallest file size. Best for screen viewing only. Images are downsampled to 72 DPI.
  • ebook - Good balance of quality and size. Suitable for most purposes. Images are downsampled to 150 DPI.
  • printer - High quality suitable for printing. Images are kept at 300 DPI.
  • prepress - Highest quality for professional printing. Minimal compression applied.

• image_dpi

  string | number

  Target DPI (dots per inch) for embedded images. When specified, this overrides the DPI setting from the preset.

  Higher DPI values result in better image quality but larger file sizes. Lower values produce smaller files but may result in pixelated images when printed.

  Common values:

  • 72 - Screen viewing
  • 150 - eBooks and general documents
  • 300 - Print quality
  • 600 - High-quality print

• compress_fonts

  boolean (default: true)

  Whether to compress embedded fonts. When enabled, fonts are compressed to reduce file size.

• subset_fonts

  boolean (default: true)

  Whether to subset embedded fonts, keeping only the glyphs that are actually used in the document. This can significantly reduce file size for documents that only use a small portion of a font's character set.

• remove_metadata

  boolean (default: false)

  Whether to strip document metadata (title, author, keywords, etc.) from the PDF. This can provide a small reduction in file size and may be useful for privacy.

• linearize

  boolean (default: true)

  Whether to linearize (optimize for Fast Web View) the output PDF. Linearized PDFs can begin displaying in a browser before they are fully downloaded, improving the user experience for web delivery.

• compatibility

  1.4 | 1.5 | 1.6 | 1.7 | 2.0 (default: "1.7")

  The PDF version compatibility level. Lower versions have broader compatibility but fewer features. Higher versions support more advanced features but may not open in older PDF readers.

  • 1.4 - Acrobat 5 compatibility, most widely supported
  • 1.5 - Acrobat 6 compatibility
  • 1.6 - Acrobat 7 compatibility
  • 1.7 - Acrobat 8+ compatibility (default)
  • 2.0 - PDF 2.0 standard