Connection Troubleshooting

The Claspt browser extension talks to the desktop app over http://127.0.0.1 (your own machine — nothing leaves your computer). On first connection each platform shows different prompts. This page walks through every dialog you might see and how to recover from each one.

Quick checklist

If the extension popup shows “Not connected”:

1. The desktop app is running — open Claspt and unlock the vault.
2. Local API is enabled — Settings → Integrations → Local API → toggle On.
3. The browser has permission to talk to 127.0.0.1 — see below.
4. No OS firewall is blocking the desktop app from accepting loopback — see below.
5. The port matches — extension Settings port number = desktop app’s Local API port.

Browser permission (http://127.0.0.1)

The extension uses an optional host permission for 127.0.0.1. You’re prompted once during onboarding to click Allow.

If you skipped or denied that prompt, grant it manually:

Chrome / Edge / Brave

1. Open chrome://extensions (or edge://extensions / brave://extensions).
2. Find Claspt — Password Auto-Fill and click Details.
3. Under Site access, set the dropdown to On all sites or add http://127.0.0.1/* as a specific site.

Firefox

1. Open about:addons → Extensions → Claspt.
2. Click Permissions.
3. Toggle Access your data for sites in the http://127.0.0.1/ domain.

Safari

The Safari version of Claspt is not currently shipped — Safari does not support the optional_host_permissions API the extension relies on. Use Chrome, Edge, or Firefox.

macOS

Application Firewall prompt

When the desktop app first binds to its local port, macOS Application Firewall (if enabled) shows:

“Do you want the application Claspt to accept incoming network connections?”

Click Allow. Localhost-to-localhost traffic on macOS is generally allowed even when the firewall is on, so this prompt is mostly a UX bump — but the dialog can block focus until dismissed.

If you clicked Deny

System Settings → Network → Firewall → Options → find Claspt in the list → set to Allow incoming connections.

If Claspt isn’t in the list yet, quit and relaunch the desktop app — macOS adds it on first listen attempt.

Notarization (first install only)

Claspt’s desktop app is signed and notarized. If Gatekeeper still blocks it (“App can’t be opened because Apple cannot check it for malicious software”), right-click the app icon in Applications and choose Open — that bypasses the warning permanently.

Windows

Windows Defender Firewall prompt

On first launch the desktop app triggers:

“Allow Claspt to communicate on these networks” with Private and Public checkboxes.

Tick at least Private networks and click Allow access. The extension only needs loopback (127.0.0.1), so Public is not required.

If you clicked Cancel

1. Open Windows Security → Firewall & network protection → Allow an app through firewall.
2. Click Change settings (admin required).
3. Find Claspt → tick Private → OK.

If Claspt is missing from the list:

1. Click Allow another app… → Browse…
2. Navigate to where Claspt is installed (typically C:\Program Files\Claspt\Claspt.exe).
3. Add it and tick Private.

SmartScreen warning (first install only)

Windows SmartScreen may say “Windows protected your PC” on the first run. Click More info → Run anyway. The Claspt installer is signed; once you’ve launched once, SmartScreen learns to trust it.

Corporate antivirus / EDR

CrowdStrike, SentinelOne, Symantec, or similar endpoint-detection products sometimes flag new applications that bind to local ports. If the desktop app starts but the extension still can’t connect:

• Ask your IT team to whitelist the Claspt binary by its signed identity.
• Check the AV’s quarantine log — if the desktop binary itself was quarantined, restore it.

Linux

Most desktop Linux distributions allow loopback traffic by default and show no prompts. The extension and desktop app should connect immediately.

If you have ufw or firewalld with strict rules

Allow loopback explicitly:

# ufw (Ubuntu, Debian)
sudo ufw allow from 127.0.0.1

# firewalld (Fedora, RHEL)
sudo firewall-cmd --add-rich-rule='rule family=ipv4 source address=127.0.0.1 accept' --permanent
sudo firewall-cmd --reload

AppArmor / SELinux

If your distro ships AppArmor or SELinux profiles that restrict desktop apps from binding to local ports, you may need to relax them for Claspt. Check /var/log/syslog or journalctl -u apparmor for denied entries.

Port conflict (EADDRINUSE)

Default port is 9315. If something else is already using it, the desktop app log shows:

Error: listen EADDRINUSE: address already in use 127.0.0.1:9315

Find the conflicting process:

# macOS / Linux
lsof -i :9315

# Windows (PowerShell)
Get-NetTCPConnection -LocalPort 9315

Either stop the conflicting app, or change Claspt’s port:

1. Desktop app → Settings → Integrations → Local API → Port → change to e.g. 9316.
2. Browser extension → Settings → Port → match the new number.
3. Click Test Connection.

Extension shows “Permission needed”

This means the optional host permission for 127.0.0.1 was revoked (typically because someone toggled it off in chrome://extensions).

1. Open the extension popup.
2. Click Allow local connection in the banner — this re-triggers the Chrome permission prompt.
3. Click Allow.

Extension shows “Vault locked”

The desktop app reachable but the vault is locked.

1. Open the desktop app.
2. Enter your master password (or use biometric unlock).
3. Switch back to your browser — the extension reconnects automatically within a few seconds.

Still stuck?

• Desktop log — the desktop app’s Settings → Diagnostics → Open Logs folder contains the API server log. Look for the most recent entries for connection-side errors.
• Browser console — right-click the extension icon → Inspect popup → Console. Errors there often tell you whether the issue is permission, port, or timing.
• Email support — support@claspt.app with the OS, browser, and the relevant log excerpt.