Your website is your #1 marketing tool.
Here's 6 ways to test your website messaging for free* before it goes live:
*note: just because these tactics are free to use doesn't mean they don't require a lot of time
Have 15-minute interviews with your current users AND your target customers [when it comes to messaging only, I'd prioritize the latter] to get their thoughts on your messaging.
Stick to basic A/B tests. If you don't yet have enough website traffic, turn to your best-performing channels. E.g. maybe you have a solid email list where you can start testing your messaging
Put together a survey with some messaging snippets ± questions to get more insights into what would make your messaging resonate with them [like getting a better idea of their needs, pains points, etc.].
With either of these "experiments", you'll want to focus on: