Not trivially. But with painstaking reverse engineering you could prove this. And people have, so you're not exclusively just taking Meta's word. The fact that Pegasus malware relied on remote code execution vuln to run malware on your phone to extract WhatsApp messages, really suggests that the E2EE works. If it wasn't E2EE, then the makers of Pegasus could have just intercepted traffic to get your messages.

Academics have also reverse engineered it as well, and though there are some weakness it's not a lie that WhatsApp is E2EE. Here's some I just found:

- https://eprint.iacr.org/2025/794.pdf

- https://i.blackhat.com/USA-19/Wednesday/us-19-Zaikin-Reverse...

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wordofx 3 days ago | parent [-]

This does not prove that Meta does not have the ability to decrypt the messages.

	▲	varenc 2 days ago \| parent [-]
		Eh, well painstaking reverse engineering is like having the source code, just 10000x more work. With that I feel like it should be possible to ensure this, or at least with some high level of confidence.