Quick answer
Quant-UX - Quant-UX wins for most builders because its free tier is perpetual and uncapped, while Proto.io’s free access is only a 15-day trial with tight project and screen limits.
How the free tiers compare
These products solve adjacent problems, but their free tiers are built for very different jobs. Proto.io is a conventional prototyping tool with a short evaluation window, then a clear jump into paid plans. It is better if you want to test a polished commercial workflow and you expect to keep using it in a team setting soon. Quant-UX is the opposite shape: it is open source, always free, and lets you keep prototyping and running user tests without a stated expiration date. The tradeoff is not just price. Quant-UX’s free tier includes research and analytics features that Proto.io’s free offer does not foreground, while Proto.io focuses on screen limits, storage, exports, and review flow. For most builders, the deciding factor is whether you need an ongoing free tool or are simply evaluating before purchase.
Proto.io vs Quant-UX free tier, side by side
| Proto.ioFTV 42 | Quant-UXFTV 90 | |
|---|---|---|
| Free access modelProto.io free access is time-limited; Quant-UX has no stated expiration. | 15-day trial, then limited free account | Always free |
| UsersQuant-UX free-tier user count is not specified in the input. | 1 user account access | Not stated |
| Active projects / prototypesProto.io caps active projects; Quant-UX does not state a prototype cap. | 1 active project | Unlimited prototypes |
| Prototype screensProto.io includes a screen limit; no matching quota is provided for Quant-UX. | 5 prototype screens | Not stated |
| StorageOnly Proto.io lists storage in the supplied free-tier data. | 10 MB storage | Not stated |
| Tests / researchQuant-UX includes testing and research in free tier; Proto.io does not list these. | Not included in free-tier items | Unlimited user tests |
| AnalyticsQuant-UX includes analytics in free tier. | Not included in free-tier items | Analytics access |
| ReviewersProto.io’s free tier limits reviewers; paid plans lift this to unlimited reviewers. | No additional reviewers | Not stated |
After you outgrow the free tier
Proto.io uses flat-rate paid tiers after the trial, starting at $29/month for Freelancer and scaling by seats and active projects up to $199/month for Corporate. Quant-UX has no paid plans listed in the supplied data, so there is no documented upgrade price to compare. For small teams, Proto.io becomes a clear subscription expense once the trial ends, while Quant-UX stays free based on the information provided. There are no usage-based scenarios to model for Quant-UX from the input.
When to pick each one
Pick Proto.io when…
- You need a short, no-card evaluation of a prototyping workflow before committing budget.
- You are comparing UI mockup tools and care about export to HTML, PNG, and PDF from the free offer.
- You only need one active project and a small prototype, such as a client demo or internal concept review.
- You expect to move to a paid plan soon and want a clear upgrade path with named tiers.
Pick Quant-UX when…
- You want an always-free tool for ongoing prototyping with no stated expiration date.
- You need to run user tests, questionnaires, and review analytics in the same product without paying.
- You are working on multiple prototypes and do not want a free-tier project or screen cap.
- You prefer open-source software and want to avoid a later pricing wall entirely.
Bottom line
For the most common builder case, Quant-UX is the better free-tier pick because it stays free, supports unlimited prototypes and tests, and does not force a quick upgrade decision. Proto.io is the better choice if you specifically want to evaluate a commercial prototyping workflow and you are fine with a 15-day trial and tight caps on projects, screens, and storage. If the goal is long-term use without payment, Quant-UX wins. If the goal is a short trial of a paid prototyping product, Proto.io is the more direct fit.
Read the full listings: Proto.io and Quant-UX. Scores use the FTV methodology at /ftv. Browse more head-to-heads on /compare, or see the top-ranked free tiers on /top.