< back to page history

This is not the most recent version of this page.
Please click here to view the current version.

Flashing checklist

Flashing checklist

Make sure your ad will pass our flashing testing

There are strict rules about the use of flashing images and regular patterns in adverts. This is to reduce the risk of exposing TV viewers that suffer from photosensitive epilepsy to potentially harmful stimuli.

Ofcom has produced guidelines on Flashing Images, see Annex 1 of the document below.

Ofcom Guidance on Harm and Offence

When you submit an ad to us, we automatically run it through a system that tests for this issue as part of the clearance process. The test is commonly known as the Harding test after the inventor of the system.

If your edit fails our flashing test, you have two options:

  • You can use our Online Flash Test service to see where in the ad the fail has occurred, amend the edit and re-submit with a new clock number. We can help you make these amends as part of our edit-to-clear service

  • Alternatively we will accept a certificate from any device on the DPP (Digital Production Partnership) list that indicates the clocked ad has passed an accepted flashing test (new from October 2018).

The certificate must display the information below.

  • Ad titleTitle Field — this must include the ad’s full clock number.
  • Duration of material tested — this ismust be the lengthexact duration of the ad.file tested including any pre and post-roll..
  • Video standardThis must be at least Standard Definition and one of the following values:
    • 576i50
    • 576p25
    • 1080i50
    • 1080p25

  • Material status — this must be one of the following values:
    • PASSED
    • PASSED (with caution)

  • TestingFrame algorithm usedRate - This must be v3.4.0either: 25 frames (if interlaced) or more50 recentframes (if progressive)
    • This is the version of the HFPA-X analysis software that the ad has been tested with.

See the full Checklist PDF document: Checklist


For further details about the Harding certificate, or general questions about testing your ad for flashing images and regular patterns, get in touch with either your Clearcast contact or Mark or Greg in the Operations team via 020 7339 4700. .

Related information: