How do you repair hairline cracks in tiles?

To repair hairline cracks in tiles, start by cleaning the area with a mild detergent and water to remove any debris. Next, fill the crack with a suitable epoxy or tile repair filler, smoothing it out with a putty knife. Allow it to cure according to the manufacturer's instructions, and then sand it lightly if necessary. Finally, you can touch up the repair with paint or sealant to match the surrounding tile.