npx skills add ...
npx skills add vercel-labs/portless --skill oauth
npx skills add vercel-labs/portless --skill oauth
Configure OAuth providers (Google, Apple, Microsoft, Facebook, GitHub, etc.) to work with portless local dev URLs. Use when setting up OAuth redirect URIs, fixing "redirect_uri_mismatch" or "invalid redirect" errors, configuring sign-in providers for local development, or when a provider rejects .localhost subdomains. Triggers include "OAuth not working with portless", "redirect URI mismatch", "Google/Apple/Microsoft sign-in fails locally", "configure OAuth for local dev", or any task involving OAuth callback URLs with portless domains.
OAuth providers validate redirect URIs against domain rules. .localhost subdomains fail on most providers because they are not in the Public Suffix List or are explicitly blocked. Portless fixes this with --tld to serve apps on real, valid domains.
When portless uses the default .localhost TLD, OAuth providers reject redirect URIs like http://myapp.localhost:1355/callback:
| Provider | localhost | .localhost subdomains | Reason |
|---|---|---|---|
| Allowed | Rejected | Not in their bundled PSL | |
| Apple | Rejected | Rejected | No localhost at all |
| Microsoft | Allowed | Allowed | Permissive localhost handling |
| Allowed | Varies | Must register each URI exactly | |
| GitHub | Allowed | Allowed | Permissive |
Google and Apple are the strictest. Microsoft and GitHub are more lenient with localhost.
Use a valid TLD so the redirect URI passes provider validation:
Any TLD in the Public Suffix List works: .dev, .app, .com, .io, etc.
Bare TLDs like .dev mean myapp.dev could collide with a real domain. Use a multi-segment TLD under a domain you control, so the app name stays clean and the domain structure lives in the TLD:
This ensures no outbound traffic reaches something you don't own. For teams, set a wildcard DNS record (*.local.yourcompany.dev -> 127.0.0.1) so every developer gets resolution without /etc/hosts, and every developer shares the same redirect URIs in the provider console.
https://myapp.devhttps://myapp.dev/api/auth/callback/googleGoogle validates domains against the Public Suffix List. The domain must end with a recognized TLD. .localhost subdomains fail this check; .dev, .app, .com, etc. all pass.
HTTPS is required for .dev and .app (HSTS-preloaded). Portless handles this automatically with --https.
Apple Sign In does not allow localhost or IP addresses at all.
https://myapp.dev/api/auth/callback/appleThe domain must be a real, publicly-resolvable domain name. Since portless maps the domain to 127.0.0.1 locally, the browser resolves it but Apple's server-side validation may require the domain to resolve publicly too. If Apple rejects the domain, add a public DNS A record pointing to 127.0.0.1 for your dev subdomain.
https://myapp.dev/api/auth/callback/azure-adMicrosoft allows http://localhost with any port for development. It also accepts .localhost subdomains in most cases. Using a custom TLD with portless is still recommended for consistency across providers.
https://myapp.dev/api/auth/callback/facebookFacebook requires each redirect URI to be registered exactly (no wildcards). Strict Mode (enabled by default) enforces exact matching.
https://myapp.dev/api/auth/callback/githubGitHub is permissive with localhost and subdomains. A custom TLD is not strictly required but keeps the setup consistent.
Set NEXTAUTH_URL to match the portless domain:
NextAuth uses this to construct callback URLs. Without it, callbacks may use localhost and cause a mismatch.
Set the callbackURL in each strategy to use the portless domain:
Set BASE_URL=https://myapp.dev in your environment.
Read the PORTLESS_URL environment variable that portless injects into the child process:
The redirect URI sent during the OAuth flow doesn't match what's registered with the provider. Check:
NEXTAUTH_URL or equivalent is set to the portless URL (not localhost)portless list to verify).dev and .app TLDs are HSTS-preloaded, so browsers force HTTPS. Start the proxy:
Portless defaults to HTTPS on port 443 (auto-elevates with sudo). Run portless trust to add the local CA to your system trust store and eliminate browser warnings.
Apple may require the domain to resolve publicly. Add a DNS A record for your dev subdomain pointing to 127.0.0.1:
Or use a wildcard: *.local.yourcompany.dev A 127.0.0.1.
The auth library is constructing the callback URL from localhost instead of the portless domain. Set the appropriate environment variable:
NEXTAUTH_URL=https://myapp.devAUTH_URL=https://myapp.devPORTLESS_URL is injected automatically; use it as the base URLSee examples/google-oauth for a complete working example with Next.js + NextAuth + Google OAuth using --tld dev.
NEXTAUTH_URL=https://myapp.devnew GoogleStrategy({
clientID: process.env.GOOGLE_CLIENT_ID,
clientSecret: process.env.GOOGLE_CLIENT_SECRET,
callbackURL: process.env.BASE_URL + "/auth/google/callback",
});const baseUrl = process.env.PORTLESS_URL || "http://localhost:3000";
const callbackUrl = `${baseUrl}/auth/callback`;portless proxy start --tld devmyapp.local.yourcompany.dev A 127.0.0.1