Short answer: before an iOS update, free space by targeting the heaviest and lowest-risk categories first. Large videos, screenshots, downloads, and obvious repeated media usually create faster room than deleting important photos in a hurry.
Pre-update cleanup is different from casual cleanup because the goal is not perfect organization. The goal is to create enough room for the update safely and quickly, without making rushed decisions you regret once the storage warning is gone.
What to delete first before an iOS update
Large videos and screen recordings that create the biggest space win fastest.
Screenshots, saved references, and low-value images.
Downloads, attachments, and files you no longer need on-device.
Obvious duplicates and repeated shots if more space is still needed.
What not to start with
Do not begin with your most important personal photos while you are under time pressure.
Do not make broad library deletions if you have not already identified the heaviest categories.
Do not spend the first pass on tiny files when a few large videos may solve the problem immediately.
A practical pre-update sequence
Start by checking the biggest media first, then move into screenshots and downloads, then review repeated photos only if the update still needs more room. That order is faster because it protects the highest-value memories while removing the heaviest clutter first.
If the main issue is heavy clips, continue to How to Find the Largest Videos on iPhone. If you want the broader route after the update warning, open free up iPhone space.
Before an iOS update, the right question is not "what can I delete fastest?" but "what creates room fastest with the least regret?"