1 B1 idiomatic informal
To have identified or discovered something important or promising.
"The scientists believe they're onto a new treatment that could change everything."
inseparable
be onto
B1 informal inseparable transitive
To have recognised or discovered something, or to have realised what someone is doing.
In plain English
To know that something important is there, or to have figured out what someone is really up to.
What does "be onto" mean?
3 meanings, ordered from most common to least. Color-coded by CEFR level.
2 B1 idiomatic informal
To have realised or suspected what someone is up to, especially when they are doing something they should not.
"The customs officers were onto the smugglers long before the arrest was made."
inseparable
3 B1 idiomatic neutral
To have recognised that something is a good idea or a winning strategy.
"With that new business model, they might really be onto something."
inseparable
Usage tip
Largely interchangeable with 'be on to'. 'Be onto something' (discovering a lead or idea) and 'be onto someone' (suspecting them) are the most common patterns. Very natural in British and American English.
Words that pair with "be onto"
Natural word combinations native speakers use most often.
something someone winner lead idea trick
How to conjugate "be onto"
The five tense forms you'll use most often.
Base
be onto
I/you/we/they
3rd person
is onto
he/she/it
Past simple
was/were onto
yesterday
Past participle
been onto
have + pp
-ing form
being onto
continuous
Hear "be onto" in the wild
Listen to native speakers using "be onto" in real YouTube videos — click a clip to watch it on Looplines.
Keep exploring
Jump to every phrasal verb built on the same verb, particle, or level.