SFR Speed Test — Fibre vs. THD Explained
SFR is France's second-largest ISP, serving over 7 million fixed broadband customers. But there is a catch that confuses millions of subscribers: SFR operates two completely different networks under nearly identical branding. One is world-class fibre; the other is legacy coaxial cable inherited from the Numericable acquisition. Your speed test results — and your experience — depend entirely on which one you have.
This matters because SFR does not always make the distinction clear in their marketing. You might pay the same price for an offer labelled "Très Haut Débit" (THD) as you would for genuine FTTH, but the upload performance is dramatically different.
SFR Fibre (FTTH) vs. SFR THD (Coaxial) — The Real Difference
| Feature | SFR Fibre (FTTH) | SFR THD (FTTLA / Coaxial) |
|---|---|---|
| Technology | Fibre-optic to apartment | Fibre to building, coax to apartment |
| Max Download | 8 Gbps (Box 8X) | 1 Gbps |
| Max Upload | 1 Gbps | 60-100 Mbps |
| Latency | 3-8 ms | 10-25 ms |
| Wall Socket | PTO (green fibre connector) | Coaxial screw connector |
| Peak Slowdown | Minimal (dedicated fibre) | Possible (shared cable segment) |
How to check which you have: Look at the cable going from your wall to your SFR Box. If it is a thin cable with a green SC/APC connector plugging into a small white wall box (PTO), you have FTTH. If it is a coaxial cable with a screw-on F-connector, you have THD. This single distinction explains why your upload speed is 500 Mbps or 60 Mbps.
SFR Box Hardware — Box 7, Box 8, and Box 8X
| Feature | SFR Box 7 | SFR Box 8 | SFR Box 8X |
|---|---|---|---|
| Wi-Fi | Wi-Fi 5 | Wi-Fi 6 | Wi-Fi 6E (6 GHz) |
| Max Wired Speed | 1 Gbps | 2 Gbps (2.5G port) | 8 Gbps (10G port) |
| 10G Port | No | No | Yes |
| Admin URL | 192.168.1.1 or monmodem | ||
| Login Method | Press WPS button 5 seconds on the box, or use sticker password | ||
The SFR Box uses an unusual authentication method: instead of a traditional username/password, many SFR models require you to physically press the WPS button on the front of the router for 5 seconds to unlock administrative access. This is a security feature that prevents remote access — but it confuses users who expect a normal web login.
SFR Box Light Guide
- Internet — Solid white: Online and working normally.
- Internet — Solid red: No internet connection. Check cables and reboot.
- PON — Red or blinking red: Fibre signal lost. The physical fibre cable between your PTO and the box is disconnected or damaged. Check the green connector at both ends.
- "S" (Sync) — Red: On THD/coaxial boxes, the "S" light indicates coaxial signal loss — similar to PON on fibre models.
- Wi-Fi — Off: Wireless is disabled. Press the Wi-Fi button or re-enable in the admin panel.
The Numericable Legacy — Why THD Exists
SFR acquired Numericable in 2014, inheriting France's largest cable TV and internet network. This coaxial infrastructure — once used purely for cable television — was adapted to deliver internet via DOCSIS technology, branded as "SFR THD" or referred to internally as FTTLA (Fibre to the Last Amplifier).
The fibre runs to a building cabinet or street node, but the final connection into each apartment uses the existing coaxial cable. This is why THD upload speeds are limited — coaxial technology allocates the majority of its bandwidth to downloads, just like cable TV always prioritised the signal coming to your television, not signals going back.
If genuine FTTH (Fibre to the Home) is now available at your exact address, you can request a migration from THD to FTTH through SFR. This often requires a technician visit to install a new PTO socket, but the performance improvement — especially upload — is dramatic.
Using Your Own Router with SFR
SFR does not officially support bridge mode or easy third-party router replacement. However, two approaches work:
- DMZ Mode: Connect your own router to the SFR Box via Ethernet. Log into 192.168.1.1, find the DMZ setting, and point it to your router's IP. This forwards all ports and avoids most double-NAT issues.
- Disable SFR Wi-Fi: If you want to use your own mesh system (Orbi, eero, Ubiquiti), disable the SFR Box's Wi-Fi entirely in settings and connect your system via Ethernet. The SFR Box continues to handle the internet connection, TV decoder authentication, and VoIP phone.
French Market Comparison
- Orange — France's #1 ISP. The largest FTTH footprint. Premium pricing, excellent Livebox hardware (6/7 with E-Ink screen), the same peering congestion issues during peak hours.
- Bouygues Telecom — Strong #3 with competitive Bbox pricing. The B&You brand offers no-contract fibre at attractive prices. Good value for price-conscious subscribers.
- Free (Iliad) — The disruptor with the Freebox Ultra offering 8 Gbps symmetrical at €49.99. Technically superior hardware (built-in NAS, VPN) but notoriously difficult customer service.
SFR support: Call 1023 (service client). Check Mon Espace Client SFR app or website for outage information and self-service diagnostics before calling.