What limitations are there on file uploads?

There is a 100 MB size limit on each file being uploaded.

The types of files which can be uploaded are:

  • Images: GIF, JPG, PNG
  • Audio: MP3, MP4
  • Documents: PDF, Word, TXT, XML 
  • Flash: SWF, FLV
  • PowerPoint

We perform manipulation techniques on all images that are uploaded, so they load as quickly as possible and use as little data as possible to download.

If you upload a JPG file...

  1. We attempt to correct the orientation of a picture, if it is upside down for example.
  2. Two thumbnails are created, with maximum widths of 100px and 300px respectively.
  3. If you have enabled the option to resize the image, this is performed at this point.
  4. We then repeatedly try to optimise the image, with varying degrees of compression, attempting to meet a maximum file size threshold for each level. For example we try a 95% compression level first, and check if the file is under 120 KB. If it's not, we try the next level at 85% and see if the file is under 150 KB, and so on. In a rare case, if after many attempts the image is still too large, it may be reduced in dimensions to no larger than 1000 x 1000, although this can be disabled by unchecking the 'Reduce dimensions of large images' option.
  5. If you're uploading large advertising creative, for example a takeover background image, you should select the option Optimise for large ad creative. A different set of compression rules will be applied to JPG files which allows for larger files.

If you upload a PNG file...

  1. It's processed through a compression level of 90 to 95%. This generally reduces file size considerably without having any noticeable affect on quality. If the resulting file is still larger than 150 KB, the same process is run again with a range of 60 to 85%.
  2. We have found in the past that many users were unintentionally uploading photographs as PNG, but it is not suitable and JPG is preferred. We cannot detect if an image consists mostly of a 'photograph'; instead, we check if a PNG is larger than 200 KB. We consider that to be unusually large for a graphic and is likely to be a photograph, and so convert it to JPG as this is a more suitable format. See the JPG rules from point 2 onwards.
  3. Two thumbnails are created, with maximum widths of 100px and 300px respectively.
  4. If you have enabled the option to resize the image, this is performed at this point.