Opening your phone will compromise its waterproof seals. Have replacement adhesive ready before you proceed, or take care to avoid liquid exposure if you reassemble your phone without replacing the adhesive.
Prepare an iOpener and heat the back of the phone along the right edge for about two minutes. This will help soften the adhesive securing the back cover.
You may need to reheat and reapply the iOpener several times to get the phone warm enough. Follow the iOpener instructions to avoid overheating.
A hair dryer, heat gun, or hot plate may also be used, but be careful not to overheat the phone—the OLED display and internal battery are both susceptible to heat damage.
Secure a suction cup to the back cover, as close to the heated edge as possible, just under the Bixby button where the adhesive is thinnest.
The suction cup will not make a good seal on the curved portion of the glass, so avoid putting it on the very edge.
If the phone's back cover is cracked, the suction cup may not stick. Try lifting it with strong tape, or superglue the suction cup in place and allow it to cure so you can proceed.
Prop up the heated edge of the phone on something that is about 0.5 inches (13 mm) thick. This will angle the phone so that the opening tool is easier to insert.
Lift the back cover's right edge with your suction cup, opening a slight gap between the back cover and the frame.
This may require a significant amount of force. If you have trouble, apply more heat to further soften the adhesive, and try again. The adhesive cools very fast, so you may need to heat it repeatedly.
If you're using an iOpener, follow the heating instructions to avoid overheating it, or the gel pack may burst.
Press the edge of an opening tool into the gap.
The rear glass can break if you use too much force or attempt to pry with metal tools.
Follow this guide to reinstall the back cover and replace the adhesive.
Be sure to turn on your phone and test your repair before installing new adhesive and resealing the phone.
If desired, you may reinstall the back cover without replacing the adhesive. Remove any large chunks of adhesive that might prevent the back cover from sitting down flush. After installation, heat the back cover and apply pressure to secure it. It won't be waterproof, but the glue is usually more than strong enough to hold.