# be onto

CEFR B2 · Phrasal verb

Source: https://englishreference.com/word/be-onto
Updated: 2026-04-24

## Definition

to discover something important or find out that someone is doing something secret or wrong.

For teachers: to be in the process of discovering a significant truth, or to have evidence of someone's illicit or hidden activities.

## Examples

- The police are onto the thief's plan.
- I think the researchers are onto a major breakthrough with this new medicine.
- The investigative journalist realized she was onto something big when the CEO refused to answer her questions regarding the offshore accounts.

## Pitfalls

- Not "He is on to a secret." but "He is onto a secret." — while 'on to' is sometimes used, 'onto' as one word is the standard form for this idiomatic meaning of discovery.

## Usage notes

- usually followed by a person (the suspect) or a noun like 'something' or 'a discovery'.
- Teaching tip: distinguish between the literal 'on to' (movement) and the idiomatic 'be onto' (discovery); the latter is often used with 'something' to mean a good idea is forming.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.