What did I see?
Most strange lights have an ordinary cause, and most of those causes can be confirmed in a minute with the right app. Answer seven questions about what you saw and the archive will give you the three most likely explanations, how to check each one, and what to do if none of them fits.
When did you see it?
If none of them fits: how to report a sighting
Write it down now
Exact time, compass direction, height above the horizon in hand-widths, how long it lasted, how it moved, any sound, and the weather. Memory reshapes all of this within hours.
Rule out the usual suspects
Flightradar24 for aircraft, Heavens-Above or Spot the Station for satellites, findstarlink.com for trains, a sky app for planets, and the American Meteor Society log for fireballs.
Keep the original file
If you have a photo or video, keep the untouched original with its metadata. Do not crop, filter or re-save it. Note what you saw with your own eyes, separately from what the camera shows.
File a report
The National UFO Reporting Center and MUFON take reports from anywhere. In France use GEIPAN; in the UK, BUFORA. Reports with times and directions are the ones investigators can actually use.
The identifier weighs your answers against the causes that account for the great majority of reports. It cannot see what you saw, and a high score is a starting point, not a verdict. For the full reasoning behind each cause, read What people actually saw.