I swear vs I swear to you

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

I swear

Informal Top 2,000 (common)

I swear to you

Top 5,000 (fairly common)

Most formal: I swear to you Most common: I swear

	I swear	I swear to you
Pronunciation	🇬🇧 //aɪ swɛər// 🇺🇸 //aɪ swɛr//	🇬🇧 //aɪ swɛə tə juː// 🇺🇸 //aɪ swɛr tə ju//
Meaning	I promise something is true	I promise you that something is true.
Example	I swear I'm telling the truth!	I swear to you, I've never seen that man before.
Register	Informal	Neutral
How common	Top 2,000 (common)	Top 5,000 (fairly common)
Collocations	swear to tell the truth, swear on my life, swear under oath	swear to you, I swear to God, swear an oath, swear on my life, swear to tell the truth
Common mistakes	Using 'swear' without 'I' (like 'swear it's true') - it sounds unnatural., Confusing with 'promise' – 'swear' is stronger and often more emotional., Forgetting to use it only in informal settings.	Using 'I swear to you' without a clear statement following it., Confusing with 'I promise you' in informal settings., Omitting the 'to you' part, making it sound incomplete.
Usage notes	Use in casual conversation to emphasize the truthfulness of a statement. It can express strong feelings. Not appropriate for formal contexts.	Used to emphasize sincerity or truthfulness. Avoid in casual contexts unless suitable for emphasis.

See it in real clips

let me say that I swear

How I Met Your Mother › S1 E1

I didn't, I swear.

let me say that I swear

How I Met Your Mother › S1 E1

I didn't, I swear.

I swear

The Lord Of The Rings › The Fellowship Of The Ring

...but I swear to you, I will not let the White City fall...

I swear to you

Frequently asked questions: I swear vs I swear to you

What's the difference between I swear and I swear to you?

I swear: I promise something is true I swear to you: I promise you that something is true.

Which is more formal: I swear and I swear to you?

I swear to you is the most formal of these.

Which is more common: I swear and I swear to you?

I swear is the most common in everyday English.

Can you show an example of each?

I swear: I swear I'm telling the truth! I swear to you: I swear to you, I've never seen that man before.

Can I use I swear and I swear to you interchangeably?

Not always. I swear and I swear to you 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.