When your Mac is connected through mobile data (phone hotspot, tethering, or a portable router) and Firefox still won’t fully load pages, it’s usually one of a few predictable blockers: DNS, proxy/VPN leftovers, captive portal weirdness, or a browser setting that’s fine on Wi‑Fi but fragile on cellular.

Metaphor of a weak link in a mobile data chain

Here’s a quick checklist first, then deeper steps if it’s still stuck.

1. Quick checklist (2 minutes)

  • Test one “known simple” site: try http://neverssl.com (plain HTTP). If that loads but HTTPS sites don’t, you’re likely dealing with DNS/HTTPS filtering, time, or a VPN/proxy issue.
  • Toggle Airplane mode on your phone/hotspot device (off/on), then reconnect the Mac to the hotspot.
  • Try Private Window in Firefox (File → New Private Window). If it works there, cookies/extensions are more likely than network.
  • Disable extensions temporarily: Firefox menu → Add-ons and themes → Extensions → toggle off ad blockers, “privacy”, antivirus web shields, and script blockers first.
  • Check if only one site fails: if one domain fails but others work, it’s often DNS, a blocklist, or the site rejecting your carrier IP range.

If nothing changes, keep going—start with the network layer so you don’t chase Firefox symptoms.

2. Confirm the hotspot connection is actually usable (beyond “Connected”)

On macOS, “Connected” can still mean you’re behind a captive portal or have a half-broken DNS route.

Hotspot network path with a highlighted bottleneck node

  • Open Safari once and visit http://neverssl.com. Some hotspots only trigger the login/terms portal in certain situations. If a login page appears, complete it, then retry Firefox.
  • Check the Mac’s date/time: System Settings → General → Date & Time → turn on “Set time and date automatically”. Wrong time can break HTTPS in ways that look like “infinite loading”.
  • Try a different DNS quickly: System Settings → Network → (your hotspot interface, often Wi‑Fi) → Details → DNS → add 1.1.1.1 and 8.8.8.8. Move them to the top, apply, then retry.

Cellular networks sometimes hand out unreliable DNS, especially when the signal is switching towers.

3. Clear Firefox’s “stuck” state without wiping everything

If Firefox works on Wi‑Fi but not on mobile data, bad cache isn’t the most common cause—but it’s quick to rule out without a full reset.

  • Hard reload a page: hold Shift and click Reload.
  • Clear site data for one problem domain: Settings → Privacy & Security → Cookies and Site Data → Manage Data… remove just the site that stalls.
  • Disable DNS over HTTPS temporarily: Settings → Privacy & Security → under “DNS over HTTPS” choose Off (or “Default Protection”). Some carriers/hotspots break DoH in inconsistent ways.

After changing DoH, fully quit Firefox (Cmd+Q) and reopen it.

4. Check for proxy/VPN settings that only break on cellular

Many “pages half-load” cases on hotspots come from a proxy setting left behind by a work tool, VPN app, or a filtering utility.

Proxy filter funnel blocking part of web traffic

  • macOS proxy check: System Settings → Network → (hotspot connection) → Details → Proxies → turn off anything you don’t intentionally use (especially “Auto Proxy Discovery” and “Automatic Proxy Configuration”).
  • Firefox proxy check: Settings → General → Network Settings → Settings… → use No proxy or Use system proxy settings (pick one consistent choice; don’t leave it on a mystery PAC URL).
  • VPN: if you use one, disconnect and test. If you must use it, try switching server region or protocol (WireGuard/OpenVPN) inside the VPN app.

If turning off proxies suddenly fixes everything, you’ve found the culprit.

5. Fix MTU/IPv6 edge cases (common on some hotspots)

This is the “everything looks fine, but some sites hang forever” category—especially on image-heavy sites or anything behind certain CDNs.

  • Toggle IPv6 for the hotspot interface: System Settings → Network → Wi‑Fi (or the active interface) → Details → TCP/IP → Configure IPv6 → try Link-local only (or turn it off if your macOS version allows). Reconnect and retest.
  • Try “safer” transport behavior in Firefox: if you’ve changed advanced settings before, consider undoing tweaks related to HTTP/3 or QUIC. (Many users changed these for speed; on some mobile networks it backfires.)

If a specific carrier network triggers the issue, IPv6/transport quirks are a real possibility.

6. Use Troubleshoot Mode to isolate extensions and hardware acceleration

This is the fastest way to answer: “Is this Firefox itself, or my add-ons/settings?”

  • Open Troubleshoot Mode: Help → Troubleshoot Mode… → Restart.
  • Test the same failing pages while connected to mobile data.
  • If it works in Troubleshoot Mode, re-enable extensions one by one (start with blockers/security tools) until the problem returns.

On some Macs, disabling hardware acceleration also helps with “blank” or “white” pages that look like network failure.

7. If nothing helps: make a clean Firefox network baseline

  • Create a new Firefox profile (temporary test): type about:profiles in the address bar → Create a New Profile → launch it and test on mobile data.
  • Try a different hotspot method: if you were using Wi‑Fi hotspot, try USB tethering (or vice versa). This changes the network path enough to confirm whether the issue is the carrier route vs. local Mac settings.
  • Restart network services (simple version): reboot the Mac and the hotspot device, then connect again before launching Firefox.

A new profile working strongly suggests a Firefox configuration/extension issue rather than “mobile data” itself.

Final thoughts

Start with the quick checklist, then prioritize DNS/DoH and proxy checks—those are the most common reasons Firefox struggles on mobile data even when the Mac looks connected.

If you can narrow it down to “only this carrier” or “only this hotspot method,” you’ll know whether to keep tuning Firefox or focus on the network path.