Internet too slow? Your right to a reduction – here's how to proceed

Section 57 (4) TKG. Sounds like bureaucratic German you'd nod along to without reading – but it's actually one of the most consumer-friendly provisions German telecommunications law has ever had. Translated, it says: if your internet connection is persistently and significantly slower than what was contractually promised, you're allowed to reduce your bill. Or terminate without notice. Your provider doesn't have to agree to this.

The surprising part: hardly anyone uses this right. Not because every connection actually delivers what's on paper – but because barely anyone knows how the proof works. That's exactly what we'll look at now, step by step.

What the law promises you

Your contract lists three speed values: the maximum, the normally available, and the minimum data transfer rate. You'll find them in the product information sheet your provider had to give you when you signed up. If you no longer have it: it's usually linked on the provider's website next to the respective plan, often right at the bottom, in tiny print.

What matters is that it's not your gut feeling ("Netflix is buffering"), but a significant, repeated deviation from these figures. And you don't establish that with just any speed test, but with the official tool of the Federal Network Agency (Bundesnetzagentur): the desktop app of breitbandmessung.de. Only their measurement report carries weight with the provider — and, if necessary, in court.

The measurement campaign: how to proceed

The process is more strictly regulated than you'd think. If you're sloppy here, you end up with a worthless report. So, step by step:

1. Install the desktop app. The browser measurement isn't enough, and neither is the smartphone app. It has to be the desktop app for Windows, macOS or Linux.
2. Connect your computer to the router via LAN cable. Wi-Fi distorts the result – and measurements taken over Wi-Fi aren't counted for the campaign at all. No LAN port on your laptop? A USB adapter costs around €15.
3. Take all other devices off the network. If someone next door is streaming or a phone on the Wi-Fi is pulling an update, you're measuring their traffic too. The app points this out, but you have to check it yourself.
4. Carry out 30 measurements on 3 different calendar days – 10 measurements per day each, with the mandatory breaks in between. The app guides you through the campaign and tells you when you're allowed to continue. Realistically, you'll need about two hours per measurement day with the computer running.
5. Download the report. At the end you get a PDF that officially documents the deviation. That's your piece of evidence.

Put simply, a "significant deviation" exists if on at least two measurement days you never once reach 90 percent of the maximum speed, if the normally available speed is undercut in too many measurements, or if the connection repeatedly falls below the contractual minimum. The app evaluates this automatically and tells you plainly at the end whether your result crosses the threshold.

Report in hand – now what?

Now you write to your provider. Not a call to the hotline where the hold music plays Vivaldi and nobody writes anything down at the end – but in writing, with the measurement report attached. You have two options:

Option 1: Reduced bill. Du kürzt die Monatsrechnung in dem Verhältnis, in dem die tatsächliche Leistung hinter der vertraglichen zurückbleibt. Kommt bei deinem 100-Mbit-Anschluss dauerhaft nur die Hälfte an, ist eine Kürzung um einen entsprechenden Anteil das naheliegende Modell: Aus 39,99 € im Monat werden dann eben rund 20 €. Der Vertrag läuft dabei normal weiter – du zahlst nur eben weniger, bis der Anbieter liefert. Kündige die Minderung schriftlich an, nenne den Betrag und verweise auf das Messprotokoll. Einfach kommentarlos weniger überweisen ist keine gute Idee; mit Ankündigung und Protokoll bist du dagegen auf der sicheren Seite.

Do the maths quickly: €20 less per month is €240 a year. That's not pocket change – and often exactly the moment the provider suddenly manages to find a technician after all. Sure, they'll show up during the classic "between 8 am and 4 pm" window, but at least things start moving.

Option 2: Extraordinary termination. You give the provider a reasonable deadline to deliver the service. If they let it pass, you're allowed to leave without observing the regular notice period – even in the middle of the minimum term. Especially if you're dissatisfied anyway, this is often the more attractive lever: the market has a lot to offer, as our comparison of DSL, cable and fibre shows.

If the provider stalls, you can bring in the arbitration board of the Bundesnetzagentur free of charge. That takes time, but it surprisingly often gets things moving – many providers give in as soon as the arbitration procedure is merely announced.

What you'll typically get as a first response, by the way, isn't a reduced bill but a counteroffer: a plan upgrade at the old price, a few months' discount, sometimes a new router. That can be fair – but don't let yourself be put off with a "we're looking into it" without a firm date attached. Set deadlines, note down every promise with date and name, and keep the measurement reports. Whoever documents things properly holds the stronger hand in this negotiation.

An honest word on success rates

Not every connection that feels like a snail actually crosses the legal threshold. Cable connections, for instance, often deliver their promised values dutifully in the morning and only drop off in the evening – if your measurement days don't capture that, the report will look better than your everyday experience. So measure when things are actually acting up for you. The campaign is spread over several days anyway, so schedule at least one measurement day for the evening.

And sometimes the result is uncomfortable too: the connection delivers what was agreed – it's just that not much was agreed. A plan advertised as "up to 50 Mbit" that delivers 45 is legally fine, but in practice it might still be too tight for your household. In that case, no reduction will help – only a better plan. Take a look at our internet comparison – or get advice via our free callback on which connection is actually available at your address.

Bottom line: the law is on your side, but it demands solid proof from you. Three afternoons of measuring against permanently overpriced bills – honestly, that's a pretty fair trade.