Free startup validation tool
Free Startup Idea Assumption Checker FREE
Find the five riskiest assumptions behind your startup or business idea, which one to validate first, and a cheap, practical way to test it. Free, no sign-up.
Test the assumption that could sink the idea
Every idea rests on a handful of beliefs: that the problem is real, that people will switch, that you can reach them, that the numbers work. Most founders test the easiest one first. This tool helps you find the one that matters most and has the least proof so far.
How to use it
- Describe the idea, and add the customer and your stage if you can.
- Press “Check my assumptions”.
- Run the suggested test for the first assumption, and use the “supports” and “challenges” lists to decide what the result means before you see it.
What you get
Five key assumptions, each marked unverified, with how consequential it is and what your description says about it (a claim, not evidence), which one to validate first, one practical test (with rough effort and time), and what evidence would support or challenge it.
Example
For a custom-cake marketplace, a critical assumption is that enough local bakers want orders through a platform rather than their own Instagram. A test: message 20 local bakers and count how many agree to list three cakes. (Illustrative example.)
Limits
The tool judges only from your description. It doesn’t know your research or your market, and its labels are judgements, not measurements.
Learn the method
Read our guide: How to Identify the Riskiest Assumptions in Your Startup Idea.
Frequently asked questions
What is a startup assumption?
Something that must be true for the idea to work but hasn’t been proven yet, for example “people feel this problem often enough to pay to fix it”.
Does it calculate my chance of failure?
No. It gives qualitative labels (Critical, High, Moderate) based on how much the idea depends on each assumption. It doesn’t calculate probabilities.
Is it free?
Yes, no card needed. 5 uses a day across all free tools without an account, 15 a day with a free account.
Does the tool treat what I wrote as evidence?
No. Anything in your description is treated as a claim, not proof. Each assumption shows whether your description doesn’t mention it, claims it, or reports a result you observed, and all of them stay marked “Unverified” until you test them with real people.
Is my idea saved?
No. It’s sent to the AI to write the answer and isn’t stored by SellTo.us.
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