let on

tell a secret or show that you know something

B2

What does "let on" mean?

To 'let on' means to reveal something that was meant to be kept secret, or to show that you know something you're not supposed to. The most common use emphasises deliberate concealment — it often appears in negative sentences such as 'she didn't let on' or 'never let on', highlighting that someone actively chose to keep quiet. When used positively, it suggests that someone disclosed something they perhaps shouldn't have. Unlike accidentally revealing a secret, 'let on' implies a conscious decision — to speak or to stay silent. It is particularly common in British and Irish English, and you will hear it most often in casual conversation and fiction rather than in formal writing.

Examples

How to use it

not let on (standalone, no object)

The most natural pattern — used when the information being concealed is already understood from context, with no need to specify it.

He knew exactly what was going on but decided not to let on.

let on that + clause

Used to specify what was revealed or kept hidden, with 'that' introducing the content (and 'that' can often be omitted in informal speech).

She didn't let on that she had already seen the film.

let on about + noun phrase

Used to indicate the topic or piece of information that was revealed or kept hidden.

Please don't let on about the promotion — I want to tell them myself.

let on to + person

Used to specify who the information was (or was not) revealed to.

Don't let on to your colleagues — the announcement is next week.

let on + question word + clause

Used when the concealed information is framed as an indirect question, often with words like 'how', 'why', 'what', or 'where'.

She never let on how nervous she felt before every performance.

Common Collocations

didn't let onnever let onlet on thatdon't let onlet on aboutlet on to anyone

Common Mistakes

Using a direct object after 'let on'

'Let on' is intransitive and cannot take a noun directly after it. To specify the secret or information, you need 'about' or 'that' to connect it.

✗ She let on the secret before the party.
✓ She let on about the secret before the party. / She let on that there was a secret.
Using 'let on' with continuous tenses

Continuous forms like 'is letting on' or 'was letting on' sound unnatural. Stick to simple tenses such as the simple past, present simple, or present perfect.

✗ He was letting on that he didn't know, but I could tell he did.
✓ He let on that he didn't know, but I could tell he did.
Confusing 'let on' with 'give away'

'Give away' suggests an accidental slip — you didn't mean to reveal it. 'Let on' implies a more deliberate choice, and is especially used in negatives to stress that someone consciously kept quiet.

Usage

This phrasal verb is more common in British and Irish English than American English. It almost always appears in negative or cautionary contexts ('don't let on', 'she didn't let on'), highlighting the idea of keeping something secret.

Frequently Asked Questions

Why is 'let on' so often used in negative sentences?

The core idea behind 'let on' is the tension between knowing something and choosing whether to reveal it. In most situations, the interesting or noteworthy fact is that someone deliberately stayed quiet despite knowing — which is why 'didn't let on', 'never let on', and 'don't let on' are by far the most common patterns. Using it positively ('she let on that...') tends to imply that the disclosure was unwise or reluctant.

Is 'let on' mainly British English? Will Americans understand it?

'Let on' is indeed more common in British and Irish English, and you are much more likely to encounter it in British novels, TV shows, and everyday speech. Most American speakers will understand it, but they might not use it naturally themselves. In American English, you would more commonly hear 'let it slip' or 'spill the beans' in similar contexts.

Can 'let on' be used in the passive, like 'it was let on that...'?

No — 'let on' does not form a natural passive construction. Because it is intransitive (it has no direct object), there is nothing to become the subject of a passive sentence. If you want a similar impersonal structure, you could say 'it emerged that...' or 'word got out that...' instead.

Can I leave out 'that' after 'let on'? For example, 'She didn't let on she was upset.'

Yes, omitting 'that' is completely natural in informal speech and writing. Both 'She didn't let on that she was upset' and 'She didn't let on she was upset' are correct, and the version without 'that' is very common in everyday conversation.

What's the difference between 'let on' and 'let slip'?

'Let slip' almost always means revealing something accidentally — the information escaped without the person intending it to. 'Let on' implies a more deliberate choice, which is why it works so naturally in negatives: 'she didn't let on' stresses that she consciously chose to say nothing.

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