I'll keep you posted vs Update

When to use each in English, with meaning, register, and examples.

I'll keep you posted

InformalTop 2,000 (common)

Update

Top 1,000 (very common)B1verb
Most formal: UpdateMost common: Update
 I'll keep you postedUpdate
Pronunciation🇬🇧 //aɪl kiːp jʊ ˈpəʊstɪd//🇺🇸 //aɪl kip jʊ ˈpoʊstɪd//🇬🇧 /["/ˌʌpˈdeɪt/","/ˌʌpˈdeɪts/","/ˌʌpˈdeɪtɪd/","/ˌʌpˈdeɪtɪŋ/"]/🇺🇸 /["/ˌʌpˈdeɪt/","/ˌʌpˈdeɪts/","/ˌʌpˈdeɪtɪd/","/ˌʌpˈdeɪtɪŋ/"]/
MeaningI'll let you know the latest news.To make something new or better.
ExampleI'll keep you posted on the project's progress.Please update the software to the latest version.
RegisterInformalNeutral
How commonTop 2,000 (common)Top 1,000 (very common)
CEFR level-B1
Part of speechverb
Collocationskeep someone posted, keep you updated, keep me informedconstantly, continually, continuously, try to, need to, on, to, with, constantly, continually, continuously, try to, need to, on, to, with
Antonyms-degrade, downgrade
Common mistakesUsing it in formal emails where more formal language is required., Confusing it with 'keep in touch', which implies broader communication.Confusing 'update' with 'upgrade', which means to improve or enhance something., Using 'updating' as a noun, instead of 'update'., Omitting the object when saying 'I will update' — it should be clear what is being updated.
Usage notesCommonly used in casual conversations to indicate you will update someone on progress or news. Less appropriate in formal situations.Use 'update' when talking about changing information to reflect new details. It's appropriate in both personal and professional contexts, but avoid using it in overly casual conversations.

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I'll keep you posted

Frequently asked questions: I'll keep you posted vs Update

What's the difference between I'll keep you posted and Update?

I'll keep you posted: I'll let you know the latest news. Update: To make something new or better.

Which is more formal: I'll keep you posted and Update?

Update is the most formal of these.

Which is more common: I'll keep you posted and Update?

Update is the most common in everyday English.

Can you show an example of each?

I'll keep you posted: I'll keep you posted on the project's progress. Update: Please update the software to the latest version.

Can I use I'll keep you posted and Update interchangeably?

Not always. I'll keep you posted and Update are related and overlap in some contexts, but they differ in register, how common they are, and usage, so swapping one for another can change the meaning or tone. Check the differences above before substituting.

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