How to Co-Witness a Red Dot Sight with Iron Sights

Co-witnessing means setting up your iron sights so they line up through your red dot's window. It gives you an instant backup if the optic ever fails and helps confirm your dot is true. Here is how it works and how to set it up.

What co-witnessing means

When a red dot is mounted at the right height, you can see your iron sights through the optic's glass. If the dot ever goes dark, you simply use the irons in the same sight picture without changing anything. There are two common styles.

• Absolute co-witness — the irons and the dot line up exactly in the centre of the window. Simple and intuitive, but the irons sit in your sight picture.
• Lower-third co-witness — the dot sits higher, with the irons appearing in the lower third of the window. This keeps your view cleaner while still allowing a fast backup.

Why mount height matters

Co-witnessing depends entirely on optic height. Many rifle red dots and holographic sights come on mounts designed for a lower-third co-witness with standard-height irons. If your optic does not include the right mount, you can add one — browse our red dot sight mounts for the correct height.

Setting it up

Fit the optic on a mount that matches your chosen co-witness style, ensure your iron sights are installed, and look through the optic. The irons should appear in the window at the expected position. Then zero the optic as normal — follow our how to zero a red dot sight guide.

Do you need to co-witness?

Co-witnessing is most relevant on rifles and carbines where a backup sighting option is valued. It is less common on pistols. If you are deciding between platforms and optic types, our guide on pistol vs rifle dot sights is a helpful starting point. Browse compatible optics in our rifle dot sights and holographic sights ranges.