Filter files

Usage example

{
  "steps": {
    "filtered": {
      "robot": "/file/filter",
      "use": ":original",
      "declines": [
        [
          "${file.size}",
          ">",
          "20mb"
        ]
      ],
      "error_on_decline": true,
      "error_msg": "File size must not exceed 20 MB"
    }
  }
}

Parameters

• interpolate

  boolean | Record<string, boolean>

• output_meta

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

• result

  boolean (default: false)

• queue

  batch

• force_accept

  boolean (default: false)

• ignore_errors

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

• use

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

• accepts

  null | string | Array<[string | string | number | null | Array<string | string | number | null>, "=" | "==" | "===" | "<" | ">" | "<=" | ">=" | rKMa06]>

• declines

  null | string | Array<[string | string | number | null | Array<string | string | number | null>, "=" | "==" | "===" | "<" | ">" | "<=" | ">=" | rKMa06]>

• condition_type

  and | or (default: "or")

• error_on_decline

  boolean (default: false)

• error_msg

  string (default: "One of your files was declined")

Demos

Related blog posts

Reject files that are larger than 20 MB:

Think of this Robot as an if/else condition for building advanced file conversion workflows. With it, you can filter and direct certain uploaded files depending on their metadata.

The Robot has two modes of operation:

• Constructing conditions out of arrays with 3 members each. For example, ["${file.size}", "<=", "720"]
• Writing conditions in JavaScript. For example, ${file.size <= 720}. See also Dynamic Evaluation.

If you want a /file/filter Step to pass every input file through unchanged, leave accepts and declines unset, or set them to null. Do not use "accepts": "true" for this: plain strings are treated as JavaScript expressions only when they use the ${...} form, such as "${true}".

Passing JavaScript allows you to implement logic as complex as you wish, however it’s slower than combining arrays of conditions, and will be charged for per invocation via 🤖/script/run.

Conditions as arrays

The accepts and declines parameters can each be set to an array of arrays with three members:

1. A value or job variable, such as ${file.mime}
2. One of the following operators: =, ==, ===, <, >, <=, >=, !=, !==, regex, !regex, includes, !includes, empty, !empty
3. A value or job variable, such as 50 or "foo"

Examples:

• [["${file.meta.width}", ">", "${file.meta.height}"]]
• [["${file.size}", "<=", "720"]]
• [["${file.size}", ">", "20mb"]]
• [["720", ">=", "${file.size}"]]
• [["${file.mime}", "regex", "image"]]

When you match against ${file.mime}, the value is typically based on Transloadit’s server-side metadata extraction in the normal upload flow, rather than only the MIME type reported by the client or browser. This makes /file/filter suitable for rejecting mislabeled files. Depending on the file container and the detection tools involved, some formats may be reported under closely related MIME types such as image/heic or image/heif.

If you only want formats that browsers consistently render, prefer an explicit allowlist such as ^(image/jpeg|image/png|image/gif|image/webp|image/avif)$ over a broad ^image/ rule.

For numeric comparisons (<, >, <=, >=), you can use human-readable byte values such as "20mb", "1gb", or "512kb". These use binary (1024-based) multipliers. Supported units: b, kb, mb, gb, tb, pb (and their IEC equivalents kib, mib, gib, tib, pib).

The includes and !includes operators work with arrays or strings (strings use substring checks).

Conditions as JavaScript

The accepts and declines parameters can each be set to strings of JavaScript, which return a boolean value.

Examples:

• ${file.meta.width > file.meta.height}
• ${file.size <= 720}
• ${/image/.test(file.mime)}
• ${Math.max(file.meta.width, file.meta.height) > 100}

As indicated, we charge for this via 🤖/script/run. See also Dynamic Evaluation for more details on allowed syntax and behavior.

Controls whether Assembly Variables are interpolated for individual instruction fields.

By default, most Robot instruction fields interpolate Assembly Variables. Set this to false to treat every instruction field as literal text, or set an individual field path to false to treat only that field as literal text. For Robot-specific fields that are literal by default, set this to true or set that field path to true to opt back into interpolation.

Use field names such as path, or dotted paths such as ffmpeg.vf for nested objects.

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

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 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 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.

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"
    ]
  }
  

• You can also tag input Steps with as to pass semantic intent to robots:
  

  {
    "use": [
      {
        "name": ":original",
        "as": "image"
      },
      {
        "name": ":original",
        "as": "mask"
      }
    ]
  }
  

Specifies the condition type according to which the members of the accepts or declines arrays should be evaluated. Can be "or" or "and".

If this is set to true and one or more files are declined, the Assembly will be stopped and marked with an error.

The error message shown to your users (such as by Uppy) when a file is declined and error_on_decline is set to true.

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 images, you can also add "blurhash": true to extract a BlurHash string — a compact representation of a placeholder for the image, useful for showing a blurred preview while the full image loads.

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

For videos, you can also add "interlaced": true to detect whether the video is interlaced. This combines the cheap ffprobe field_order flag with a bounded idet sampling pass over the first frames of the source, exposing interlaced, field_order, and a diagnostic interlace_detection object under file.meta. This is computationally expensive and billed accordingly.

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.

Files that match at least one requirement will be accepted, or declined otherwise. If the value is null, all files will be accepted. If the array is empty, no files will be accepted. Omit this parameter or set it to null when you want the Step to pass every file through. Examples:

[["${file.mime}", "==", "image/gif"]] [["${file.size}", "<", "5kb"]]

For numeric comparisons (<, >, <=, >=), human-readable byte values such as "20mb", "1gb", or "512kb" are supported.

If the condition_type parameter is set to "and", then all requirements must match for the file to be accepted.

If accepts and declines are both provided, the requirements in accepts will be evaluated first, before the conditions in declines.

Files that match at least one requirement will be declined, or accepted otherwise. If the value is null or an empty array, no files will be declined. Examples:

[["${file.size}", ">", "1024"]] [["${file.size}", ">", "20mb"]]

For numeric comparisons (<, >, <=, >=), human-readable byte values such as "20mb", "1gb", or "512kb" are supported.

If the condition_type parameter is set to "and", then all requirements must match for the file to be declined.

If accepts and declines are both provided, the requirements in accepts will be evaluated first, before the conditions in declines.