An onsight and a flash are both clean first-try ascents — the difference is information. An onsight uses no prior knowledge at all; a flash allows beta, such as watching someone climb it or getting hold-by-hold tips. Onsighting is the purer, harder achievement at the same grade.
| Aspect | Onsight | Flash |
|---|---|---|
| First try | Yes | Yes |
| Prior information | None at all | Beta allowed |
| Difficulty | Harder | Slightly easier |
| Tests | Route-reading + climbing | Climbing (with beta) |
| Prestige | Highest first-try style | High |
It's an onsight if…
- You had zero prior information
- You didn't watch anyone on it
- You sent it clean, first try
It's a flash if…
- You used beta or watched someone
- You studied a video first
- You sent it clean, first try
Verdict
Frequently asked questions
What's the difference between an onsight and a flash?
Both are clean first-try ascents, but an onsight has no prior information at all, while a flash allows beta — watching others, hold descriptions, or video. The lack of any foreknowledge makes the onsight the higher achievement.
Is a flash harder than a redpoint?
At the same grade, usually yes. A flash gives you one shot with gathered beta, while a redpoint lets you rehearse the moves over many attempts. So flashing a grade is a bigger achievement than redpointing it.
Does watching a video ruin an onsight?
Yes — any prior information, including video, hold-by-hold beta, or watching someone climb it, means a clean first try counts as a flash rather than an onsight. Onsighting requires going in with nothing.