When comparing these two products, the main differences that stand out are cost, plan limits, and overall design philosophy. Their feature offerings are pretty similar.
Headlessforms' cheapest monthly plan starts at $28/month with 1,500 submissions and 15 forms. Compare that to Submit JSON's $15/month plan that has a submission limit of 10,000 with 100 forms.
Submit JSON's plans offer almost 10 times (1000%) the submissions on average with a comparable feature set.
Headlessforms comes with a few bells and whistles that Submit JSON will not ever have, like a form builder. It's definitely targeted more towards non-technical folks.
Regardless, it's another Formspree clone. Headlessforms's HTML-first approach is their greatest strength, and also their greatest weakness.
In comparison, Submit JSON's API-first approach is more versitile, secure, and aligned with modern web development best practices.
Which is the best form backend for you? We think the answer is obvious, but we'll let you decide.