OutSystems is the best AI app builder for a production app customers will log in to, because it counts external users as their own category and sells uptime and support as part of a governed platform. A custom build by Black Badger ranks second, and it is the stronger choice when the customer app is part of what you sell and you want to own it outright.
The ranking, entry by entry
1 OutSystems
Best for customer apps run by a company with its own developers
A customer-facing app raises questions an internal tool can avoid, such as what happens when it is down and what each outside user costs. OutSystems is first because its model answers both. External end users are counted separately from internal ones, default uptime is stated at 99.5 percent, and a 99.95 percent level and 24x7 support are sold as add-ons. You need developers to use it well.
Watch for. Nothing is priced on the page. Get the quote with your actual number of external users, and ask what each add-on costs before you compare.
- How it charges
- Quoted by app size, end users and add-ons
- Main limit
- Price rises with app size, user count and add-ons, and is quoted.
2 Custom build by Black Badger
Best for customer apps that are part of what the company sells
When customers log in, the app is part of your product, and a rented platform sets part of its price and its limits. A custom build ranks second because Black Badger builds the portal or app with your own sign-in, data rules and branding, and hands you the code and the hosting account. A thousand customers logging in adds no license cost, and you pay only the running costs of the services underneath.
Watch for. You become the owner of a production system, so name the person who will answer when a customer reports a problem. The scope covers who maintains it.
- How it charges
- One-time build scoped in writing, then running costs such as hosting
- Main limit
- Needs a scoping call first, and suits companies of 50 or more employees
What a custom build involves, and how to ask about one
3 Retool
Best for portals for a known set of outside users on existing data
Retool ranks third. It is known for internal tools, but the Business plan adds external users, and the first 50 are free. From 51 to 250 they are billed per external user, yearly. That makes it a practical way to give a known set of customers or vendors a portal onto data you already hold, as long as the audience stays in the hundreds.
Watch for. The published external user price stops at 250. Past that the price comes from sales, so ask early if your customer base is larger.
- How it charges
- Per builder and per internal user, billed yearly or monthly
- Main limit
- SSO, SCIM, Git source control and granular roles are Enterprise only.
4 Lovable
Best for launching a first customer app quickly to test demand
Lovable is fourth for customer-facing apps. It can put a working app in front of customers quickly, and credit pricing means the bill does not grow with the number of people who log in. It ranks below the top three because the permission model for a generated app is yours to define through row-level security policies, and a mistake there is visible to customers.
Watch for. Have someone who understands data access review the policies before real customer records go in. Audit logs are listed only for Enterprise.
- How it charges
- By credits, not seats, in monthly tiers
- Main limit
- SSO is Business only. Audit logs and SCIM need Enterprise.
5 Replit
Best for small teams that want the app built and hosted in one place
Replit ranks fifth here. Building and hosting in one place is attractive for a first customer app, and production databases are offered on paid plans. The reason for caution is how hosting is billed. Published apps are metered on outbound data transfer, compute units and requests, so a busy customer app has a bill that moves with traffic.
Watch for. Repeated payment failures can lead to suspension of published apps. Put billing for a customer-facing app on an account finance watches.
- How it charges
- Monthly or yearly plan with credits, plus metered usage
- Main limit
- Pro caps at 15 collaborators. SSO, SCIM and audit logs are Enterprise.
6 Bolt.new
Best for prototypes a team plans to move to its own hosting
Bolt.new is sixth. Its strength for this question is that the app can leave. A team can claim the database Bolt creates, connect it to Supabase and move the app to hosting it controls. A customer app should end up on hosting its owner controls. Every project gets a free bolt.host subdomain, and custom domains need a paid plan.
Watch for. SSO, audit logs and data governance and retention policies are listed under Enterprise, which has no published price.
- How it charges
- Per member, monthly, Enterprise custom priced
- Main limit
- Tokens are per member and not pooled. SSO and audit logs are Enterprise.
7 Base44
Best for A self-contained app with login and hosting already included
Base44 ranks seventh. The vendor says authentication, a managed backend and hosting are built in, so a customer login exists from the start without extra setup. It is last on this list because the pages we read do not say where app data is stored. A company putting customer records in an app has to be able to answer that question.
Watch for. Message credits are capped by plan, from 100 on Starter to 1,200 on Elite, and heavy building uses them quickly.
- How it charges
- Monthly by plan, billed yearly, with message credits
- Main limit
- Message credits are capped per plan. SSO is Enterprise only.
How this list was ranked
We ranked for an app that people outside the company sign in to, such as a customer portal, a vendor portal or a booking and ordering app. What each outside user costs counted first, then what the vendor says about uptime and hosting, then how much control you keep over the data and the exit.
Where a vendor publishes nothing on a point, the entry says so and does not guess.