Best AI App Builder for Client Portals (2026): Your Client Is Not a Teammate

Quick Answer

If you are building a portal for your clients, the auth column tells you nothing. Seven of the eight builders we track ship some form of login. The question that decides a client portal is narrower and almost nobody asks it: does the product have a first-class idea of a person who uses your app without being on your team, and where does that person's account actually live?

Three of eight name the distinction in their own documentation. One built a billing model on it and retired that model in August 2024. One removed app-side logins entirely in January 2026. On the remaining three, your clients are not the builder's problem at all, because the identity layer belongs to somebody else.

Shortlist for September 2026: Softr if you want the separation handed to you, with the caveat that the mechanism sits on a higher plan tier. Base44 if you want the tightest built-in model of who can open the app, with the caveat that its default visibility setting is the wrong one for a portal. Lovable if your portal needs enterprise sign-in for your clients' own IT departments. Everything else is a build, not a feature.

The column that decides nothing

Every comparison of these products has an auth row and it is a row of yeses. We wrote a whole piece on why that row is useless on its own, covering whose login screen your users are signing into, and the same emptiness shows up here in a sharper form.

A login is generic. A client portal is not. A client portal has a shape that internal tools do not:

• The people signing in are outside your organisation. They do not have your email domain, they will not be in your identity provider, and you cannot walk over to their desk.
• There are more of them than there are of you, and the number grows as the business grows.
• Each of them must see only their own material, and a mistake is not an inconvenience, it is a disclosure.
• They will judge your business by the thing they log into, so whose brand is on it matters.

Every builder has a well-trodden path for the first kind of user, your teammate. Not all of them have a path for the second. Confusing the two is the single most expensive mistake available here, because the wrong choice does not fail loudly. It ships, it works in testing with your own account, and it goes wrong the first time a client sees a row that is not theirs.

Eight builders on the distinction a client portal turns on

Every cell above comes from the vendor's own documentation, read on 21 September 2026. Where a cell says a thing is not documented, that is an absence in the documentation we read, not a claim that the product cannot do it.

The one that built a billing model on your clients, then retired it

Softr is the only product of the eight that ever gave "your client" a formal, billable existence, and its documentation for that model is still live with a warning on top.

The mechanism was disarmingly literal. An internal user was one who shared an email domain with any workspace collaborator, or whose domain was whitelisted for signup. An external user was everyone else. The docs walk through it with an applicant tracking system: the head of HR at company XYZ is internal, HR managers on the same domain are internal, and applicants on other domains are external.

Read that again from a portal builder's point of view. Whether your client counted as a client was decided by their email address, not by anything you configured.

Then, in the vendor's own words:

Softr, verbatim: "Note that the Internal/External User distinction is only applicable to legacy V3 pricing plans available before August 13, 2024. Current V4 pricing plans do not distinguish between internal and external users."

So the industry's one attempt at making "an outsider who uses your app" a billing object lasted until August 2024 and was withdrawn. What survives on Softr is the access half rather than the billing half, and it is genuinely good: the permissions documentation names Client Portal as a use case by name, and custom user groups can be dynamic, keyed on user attributes or subscription tier, so a client lands in the right group on login without you touching anything.

The gate is worth knowing before you build. Softr's default groups are only two, non-logged-in users and logged-in users. Everything finer than that is a custom user group, and custom user groups are documented as available on the Professional, Business and Enterprise plans. The thing a client portal exists to do is not the entry-level behaviour.

The default that is wrong for a portal

Base44 has the cleanest built-in model of who can open an app. Three visibility levels, stated plainly: Public (anyone on the internet, no sign-in), Private (only invited people, sign-in required), and Workspace (everyone in your Base44 workspace, sign-in required).

It also draws the line we care about explicitly, and in the right place:

Base44, verbatim: "Only collaborators and the app owner can access the app editor and your app's dashboard. Roles such as Admin and User control what people can do in the live app, but they do not give access to the app editor or dashboard."

That is the teammate-versus-client distinction stated as a product rule rather than left to you.

Two things then decide whether it fits. First, Private apps are available on paid plans only, so the mode a client portal needs is not the mode you can evaluate for free. Second, and more quietly, Base44 uses what it calls smart app visibility to suggest a starting point, and apps that look like public sites are automatically set to Public without requiring login. You can change it at any time. You have to notice first. A portal that ships on the wrong setting is not a misconfiguration, it is an open filing cabinet.

Note also what the plan documentation meters: message credits, integration credits and app count. There is no user count in it. Base44 is not counting your clients, which is a relief for the bill and a reminder that the constraint lives elsewhere.

The builder that separates the three identity questions for you

Lovable is the only one of the eight whose documentation goes out of its way to stop you conflating the identity features, and it does so with a table that is worth stealing as a checklist for any platform:

• Workspace identity reuse controls whether apps you build can recognise a workspace member who is already signed in to Lovable. Audience: your workspace members.
• Workspace SSO controls how your team signs in to Lovable itself. Audience: your team.
• SAML SSO for apps controls how external end users of a published app sign in with their own company credentials. Audience, in the vendor's own phrasing, "your app's outside users".

Only the third is a client portal feature. The first is the internal-tool answer, and the docs say so directly, listing an employee portal and a workspace-only PTO app as the fits, then routing you away: for customer-facing apps, public signup flows, or apps whose users have no Lovable account, use traditional app authentication instead.

The asymmetry to price in is at the bottom of the SAML page. For your app's end users, sign-in is service-provider-initiated only. Your client must start from your app. Starting from a tile in their own identity provider's dashboard is not supported for app end users, and it is supported for workspace SSO. The outsider path is real, documented and deliberately narrower than the teammate path.

Where the outsider is somebody else's object entirely

On four of the eight, the builder has no concept of your client at all, and that is not necessarily a mark against them.

Bolt.new surfaces users through a database settings panel. You get a sign-ups graph, the most recently added users, invite-by-email, create and delete, and search by email or ID. Useful, and revealing: your clients are rows you administer, not a platform object with its own rules.

Bubble is philosophically similar and much older about it. A user is "just another data type", with three built-in fields that cannot be changed or deleted and are identical across every Bubble application: Email, Password and Email confirmed. The password is one-way hashed and salted and "invisible even to you as the app developer". Bubble also creates temporary users for visitors who have not signed in, carrying their data forward if they later register. For a portal that is a detail worth planning around rather than discovering.

Replit is the interesting case because it gives you the choice explicitly and tells you how to make it. Replit Auth means your users sign in with existing Replit accounts and the sign-in page is Replit-branded. Clerk Auth gives your app "its own dedicated Clerk tenant" where "users create accounts inside your app, not Replit". For a client portal the first option asks a professional service client to open an account with a developer platform they have never heard of in order to read their own documents. That is not a technical objection. It is a conversion one.

v0 does not attempt it. Its documentation routes identity to Marketplace integrations such as Supabase, Neon and Upstash, and your client belongs to whichever of those you install. Nobody at v0 is counting your clients, which also means nobody at v0 can tell you what they cost.

Webflow is the clean negative. Its developer documentation index, read on 21 September 2026, contains zero entries for user accounts, app users, membership, signup or login. App-side user accounts were removed on 29 January 2026, a change we covered when it landed. Webflow remains excellent at the marketing site that sits in front of a portal, and it is not the portal.

The part that is not an auth question at all

Deciding who may hold an account is only half of it. The other half is whether one client's rows can ever reach another client's screen, and that is a separate mechanism with a separate failure mode. We measured it across the same eight in per-user is not per-tenant, and the short version is that showing a user their own rows is the easy case, while keeping two organisations apart is the one that only one builder documents as a supported pattern.

A client portal needs both. Pick for identity and you can still leak. Pick for isolation and your clients may not be able to log in without help. There is no builder here where one column answers both.

Verdict, September 2026

Softr is the strongest fit if the portal is the product and you want the separation as a feature rather than a build, budgeting for a Professional plan or higher because custom user groups are where the separation actually lives.

Base44 is the strongest fit if you want the visibility model built in and stated plainly, provided the first thing you do after generating the app is check that visibility is Private rather than the Public value smart visibility may have chosen for you.

Lovable is the strongest fit when your clients are businesses whose IT departments will want to bring their own identity provider, with the service-provider-initiated limit understood in advance rather than discovered during a rollout.

Replit and Bolt.new are both credible if you are comfortable owning the identity layer, Replit by choosing Clerk over Replit Auth so your client never sees a developer platform's branding, Bolt by treating the user list as what it is, a database you administer.

Bubble rewards the investment if you already know it, because a user being a data type is a constraint and a superpower at once.

v0 is a fine choice for the portal's interface if you have already decided where identity lives.

Webflow is not in this category any more, and the honest recommendation is to use it for the site and put the portal somewhere else.

What to check before you commit

1. Open the plan documentation and find the word that means "the people who use what I built". If it is absent, the builder is not metering your clients and somebody else is.
2. Find the default visibility or access setting for a new app and write it down. Assume it is wrong for a portal until you have read it.
3. Ask whether the fine-grained grouping you need is available on the tier you intend to buy, not on the tier in the marketing table.
4. If enterprise sign-in matters, check which direction it runs, and whether the app path has the same capabilities as the team path.
5. Decide, before you build anything, whether one client seeing another client's row is an embarrassment or an incident. That answer sets your isolation budget.