Is it possible to pass very long params to a suitelet? I've encoded an image to a string thats ~30,000 characters. I want to send that string to a suitelet that would take it, and decode it back into an image.

One option would be to store the string in a file and pass the file ID as the parameter instead.

If you're sending the parameter from a suitelet you can save the string to a "long text" field

So the string exists on our Non-NetSuite eCommerce site. Wanting to send that to a NS suitelet. I thought a Fetch or XMLHttpRequest would work but both still give me an error about being too big

Are you POSTing to the suitelet? 30,000 characters shouldn't be an issue for the request there. Is the error something within NetSuite or before it gets to that point?

This might not be a today project. didn't even think about CORS limitation. Was testing in the console on a netsuite page. Once I go to our eCommerce site, I'm going to run into CORS issues