Metadata

Many files contain interesting information about their contents. This is called "metadata". Transloadit automatically extracts this metadata for all uploaded, imported, and processed files.

At the very minimum, each file will have the information such as:

{
  "id": "ae52b7f8c1b3426e8c29ea0a9daf8306",
  "name": "straw-apple.jpg",
  "basename": "straw-apple",
  "ext": "jpg",
  "size": 92230,
  "mime": "image/jpeg",
  "type": "image",
  "field": "test_file",
  "url": "http://tmp.maynard.transloadit.com/upload/1324a798a99fce7f5f8289a95a74f02b.jpg",
  "original_id": "4af24fb2595f44809f3adc2f77bc9bfa",
  "meta": {
    // …
  }
}

The information we can extract depends on the media file, its type, but also who produced it. If it was an iPhone, there's probably latitude in there for geo-positioning. More common keys include height, and duration.

To see what information we can extract from files that you will throw at us, you could try one of our demos and inspect our response after uploading a file there.

id: A random and unique ID used internally by Transloadit to track the file.
name: The name of the file. Transloadit will change the extension used for this field if the file undergoes processing into a different format.
basename: The name of the file without the extension.
ext: The extension of the file.
size: The size of the file, in bytes.
mime: The determined MIME type for this file.
type: An abstract type describing the file, which can currently be "image", "video", "audio", or null.
field: The name of the form field used to submit this file.
url: The URL at which this file can be accessed. This is either a URL in your S3 bucket, or a temporary URL on our servers. Since temporary URLs expire after a few hours, you should make sure to move your files elsewhere unless you are using a storage robot.
original_id: The unique ID of the original upload file from which this file was generated. This is useful to determine which file of a multi-file upload was used to generate a given file, after several Steps of processing.
meta: An object containing additional metadata extracted from the file, as shown below.

Image Metadata

Although it depends on the file at hand, files whose mime type is image can typically contain data such as the following inside the meta property:

width: The width of the input image, in pixels.
height: The height of the input image, in pixels.
aspect_ratio: The aspect ratio of the image, which is its width divided by its height. Will be 0 if for some reason the image height is 0.
date_recorded: The date and time at which this image was taken, in the format YYYY/MM/DD HH:MM:SS TZ, such as "2010/06/30 22:16:06 GMT".
date_file_created: The creation time for the file system.
date_file_modified: The modification time for the file system.
title: The title of this image, such as "Tree".
keywords: An array of keywords for this image, such as ["tree", "nature"].
description: A description of this image, such as "This tree is very old.".
location: The location at which this image was taken, which is usually the street, such as "Zingster Str. 32".
creator: The creator that took the image.
author: The author that took the image. Some cameras populate this field as opposed to creator.
copyright: The copyright metadata field.
copyright_notice: The copyright notice metadata field.
city: The city in which this image was taken, such as "Berlin".
state: The state in which this image was taken, such as "Berlin".
country: The country in which this image was taken, such as "Germany".
country_code: The country code of the country in which this image was taken, such as "de".
aperture: The aperture setting for this image, such as 5.7.
exposure_compensation: The exposure compensation for this image, such as "+4/3".
exposure_mode: The exposure mode for this image, such as "Auto".
exposure_time: The exposure time for this image, such as "1/30".
flash: The flash settings for this image, such as "Off, Did not fire".
focal_length: The focal length for this image, such as "55.0 mm".
f_number: The f-number for this image, such as 5.6.
iso: The ISO value for this image, such as 800.
light_value: The light value for this image, such as 6.9.
metering_mode: The metering mode for this image, such as "Multi-segment".
shutter_speed: The shutter speed for this image, such as "1/32".
white_balance: The white balance setting for this image, such as "Manual".
device_name: The device name of the camera, such as "iPhone 3GS".
device_vendor: The camera manufacturer, such as "Apple".
device_software: The version of the device software for the camera, such as "3.1.2".
latitude: The latitude at which this image was taken, such as 52.5374.
longitude: The longitude at which this image was taken, such as 13.4034.
thumb_index: The index of the current thumbnail starting at 0. This key is only present for results of 🤖/video/thumbs.
thumb_offset: The offset for the current thumbnail, in seconds. This key is only present for results of 🤖/video/thumbs.
frame_count: The number of frames in an animated GIF file. This is 1 by default for all other image types.
colorspace: The colorspace of the image. This could be "sRGB" or "Gray" for instance. In Transloadit's first ImageMagick stack version, there's a bug which would make the colors used in an image determine its colorspace, and a grayscale colored image would report "Gray", even if saved as "RGB".
has_clipping_path: Is 1 if the image contains a clipping path, 0 otherwise.
average_color: Not to be confused with dominant color, that counts a single most occurring pixel color and has limited use cases. The average color is calculated by first scaling the input image to 1 pixel.
has_transparency: Returns true for images that have transparent areas. This key is only returned if you set output_meta.has_transparency to true.
dominant_colors: Returns an array of the 20 most used colors for images. This key is only returned if you set output_meta.dominant_colors to true.

Video Metadata

Although it depends on the file at hand, files whose mime type is video can typically contain data such as the following inside the meta property:

width: The width of the video, in pixels. If the video was meant to be displayed with a different display ratio than the pixel ratio, this indicates the width at which the video is to be displayed.
height: The height of the video, in pixels.
framerate: The frame rate of the video, such as 29.5.
video_bitrate: The video bit rate of the video, such as 500000.
video_codec: The video codec of the video, such as "ffh264".
audio_bitrate: The audio bit rate of the video, such as 128000.
audio_samplerate: The audio sample rate of the video, such as 44100.
audio_channels: The number of audio channels in the video, such as 2.
audio_codec: The audio codec of the video, such as "faad".
seekable: Whether the format of the video supports seeking, such as true.
colorspace: The colorspace of the video. This could be "sRGB" or "Gray" for instance. This key is only returned if you set output_meta.colorspace to true.
date_recorded: For details, see the description for image metadata.
date_file_created: For details, see the description for image metadata.
date_file_modified: For details, see the description for image metadata.
device_name: For details, see the description for image metadata.
device_vendor: For details, see the description for image metadata.
device_software: For details, see the description for image metadata.
latitude: For details, see the description for image metadata.
longitude: For details, see the description for image metadata.

Audio Metadata

Although it depends on the file at hand, files whose mime type is audio can typically contain data such as the following inside the meta property:

duration: The length of the audio file in seconds.
audio_bitrate: Bits per second (for all channels combined).
audio_samplerate: The audio sample rate in Hertz, such as 44100, for a CD.
audio_channels: Number of channels. Typically 2, for stereo.
audio_codec: The Audio codec used. Here's a list of all audio codecs that Transloadit supports.
artist: Many applications that produce audio write additional information into the audio file such as artist, year, album, genre.
mean_volume: The mean volume of the audio file. This key is only returned if you set output_meta.mean_volume to true.