Which AI app builder is safest? We scanned 30,998 apps

You picked a builder before you knew anything about any of them. Maybe a thread recommended one, maybe you liked the demo, maybe it was the one your friend used. And somewhere since then you have seen someone claim that the one you picked is the insecure one, and wondered whether the safest AI app builder was one of the others all along.

So we measured it. In August 2026 we scanned 30,998 live apps published from Lovable, Base44, Replit, v0 and Bolt, and ran the same nine external checks on every one of them.

Here is the part the comparison posts get wrong: the builder you chose is almost never what decides whether your app is exposed. All five came back between 99% and 100% for at least one finding. The real differences between them are wide, and they are differences in defaults rather than in safety.

Which AI app builder is safest?

None of them, and the ranking you are looking for does not exist.

Every builder in this scan produced apps with findings, at close to the same rate, because the commonest finding is set by the hosting rather than by the person who built the app. Below that headline the builders diverge sharply, but they diverge on things like whether your source code gets published alongside your app, not on whether strangers can read your users.

The thing that separates an A from a D is something you did after you picked a builder. Usually it is one decision: you connected a database.

What we measured

The same nine checks we would run on your app, read from outside, with no login and no access to anyone's account.

We scanned every app between 12 and 14 August 2026, and 30,998 of them produced a result we could classify. Every percentage below is a share of the apps that check actually answered on, never a share of everything we scanned. A check that could not complete is recorded as unknown, not as a pass, which is why the denominators in the tables move around. The full method and the underlying data are in the report.

Two things we did not do. We never logged in anywhere, and we never read anyone's rows: where a table answered, we asked the database how many rows it would hand over and stopped there. No app is named here or anywhere else we publish.

Every builder is at 99%, and that number says less than it looks

Because nearly all of it is one finding, and that finding belongs to the platform.

Missing browser security headers turned up on 18,539 of 18,554 Lovable apps, all 5,438 Base44 apps, 1,790 of 1,790 v0 apps, 1,121 of 1,123 Bolt apps and 2,924 of 3,042 Replit apps. Headers are sent by whatever serves your app, so on a builder's own domain they are a property of that domain and identical across every app sitting on it.

It is a real finding and it is worth closing when you move to your own domain. But it is the least urgent line on a report, and it is most of what "99% of apps have a problem" is counting.

The real difference between builders is defaults

Each builder ships a different set of defaults, and those show up in nearly every app it makes.

The source-map column is the one to read carefully, because on Base44 it is not measuring the same thing as it is on the other four. We re-opened 30 flagged Base44 apps in September: on 27 the only map answering was /static/js/badge.js.map, which belongs to Base44's own badge script, and on none of the 30 did a map cover the owner's files. So that 59% is a platform publishing one of its own files on every app it hosts, not 3,229 owners leaking their code. On Lovable, Replit and Bolt the same column does mean the owner's code, which is why 1% and 6% and 59% cannot be read down the page as a ranking. What we found inside those Base44 maps is the full account.

The 99% cross-origin column is the real one, and it is also Base44's own doing: the platform sets CORS for every app it hosts and offers no per-app setting. Published source code, where it is yours, means the original files behind your app are readable from the browser's developer tools. What that does and does not expose is worth reading if you are on one of the other four.

The secret-key column is the one people expect to dominate, and it does not. A key worth naming turned up in 4% to 7% of apps on three of the five builders and in none of the v0 apps at all.

If you want the plain-language version for the builder you actually use, each has its own page: Lovable, Base44, Replit, v0 and Bolt.

Or skip the reading: our free scan runs these same checks against your live site and tells you which of them your app trips. About 20 seconds, no account: scan your app.

What actually decides a D or an F

A database, and what you did to it.

Lovable produced 407 apps graded D or F out of 18,554. v0 produced none out of 1,790. That looks like a verdict on the two builders until you look at what the apps are: 35% of Lovable apps name a database project, against roughly 1% of v0 apps.

The checks that can produce a D or an F are almost all database checks. An app with no database has less that can go wrong and less for us to look at. So the Lovable row is not measuring a worse builder, it is measuring a builder whose users connect databases, which is most of why people choose it.

Of the 3,553 Lovable apps whose database answered us, 2,017 had at least one table a stranger could read with no login. That is the finding worth fixing first, and it has nothing to do with which builder generated your front end.

Lovable is where that number is big enough to be worth its own article: what 18,554 live Lovable apps showed takes the same nine checks through the largest cohort we have.

Why we are not going to rank them

Because for three of the five, we could not check enough databases to say anything at all.

Here is the part of the data that every league table leaves out:

Look at the Base44 row. More than a quarter of its apps name a database project, and exactly two of those databases ever answered us. We are not going to turn two apps into a rate and print it next to a number built on 3,553. Nor is anyone else who has scanned from outside, whether or not their comparison table says so.

What to check on your own app

All of this is checkable by hand. Keeping the answer true next month is the part that does not stay done, and it is why Reeve Care exists: it re-runs these same checks on a schedule and tells you when an answer gets worse, then keeps verified copies of your database outside your database provider's account so there is something to put back. That second half matters because we only ever check reading, and the same permissive rule that lets a stranger read a table usually lets them write to it. What it watches and what it costs.

If you would rather work through this as a list, the 10-minute security checklist covers the whole set in plain language.