Reader question: How do I get from a single Wi‑Fi speed test to the intended proof of underperformance for my German fixed‑line contract?
The connection in the study is regularly too slow. Your private speed test yields low values, the provider refers to the contract and possible influences inside the flat. For a legal review of underperformance of your German fixed‑line contract you need more than a screenshot of a single Wi‑Fi test.
§ 57 paragraph 4 TKG links the corresponding rights for internet access to substantial, continuous or regularly recurring deviations and a monitoring mechanism provided for that purpose. [TKG57] The Bundesnetzagentur provides such a proof route for fixed‑line via the Breitbandmessung desktop app. [BNetzTempo]
Use the correct contractual values
For the actual tariff look up the maximum, normally available and minimum data transfer rates for download and upload. Use product information, contract documents and, if applicable, individually confirmed changes. The guidance explains tariff selection and, if necessary, manual entry. [BNetzHand]
An advertising figure for a product now newly offered must not unnoticed replace your own contractual values. Also check that you are using the fixed‑line proof procedure. A mobile tariff and its separately introduced procedure since 2026 are not treated here with the same measurement instructions.
Agree the measurement environment in advance with the household
The guidance requires, among other things, a suitable direct LAN connection from the measuring device to the router and from there to the network termination. Wi‑Fi or powerline intermediary paths do not fit this proof setup. Concurrent traffic, VPN rerouting, power‑saving settings and the capability of the measuring device must also be considered. [BNetzHand]
Therefore arrange the measurement times in advance with flatmates. Someone who currently needs an important connection should not be unexpectedly interrupted by the necessary measurement environment. A condition confirmed only in the input window must actually be established as well.
Use the full current instructions rather than bypassing an error message by an incorrect confirmation. For a borrowed or managed computer, required changes should be agreed with the responsible person.
Plan a complete campaign
The current fixed‑line information requires 30 measurements within 14 days, distributed across three measurement days with ten measurements each. There must be at least one calendar day between measurement days. Within a measurement day there are generally at least five minutes between measurements; between the fifth and sixth measurement at least three hours. [BNetzTempo]
For a hypothetical household plan you could reserve three suitable, sufficiently separated days and keep two measurement blocks with ample spacing free on each. After the actual campaign start check the remaining time in the app. A calendar entry is not yet a complete measurement day; missing individual measurements are not supplemented from memory.
Why the first repeat attempt is not sufficient
In the fictitious case a resident initially measured only in the evening via a Wi‑Fi repeater while another device was transferring large amounts of data. This observation may explain her everyday annoyance. But it does not replace the prescribed measurement environment and complete campaign.
She therefore collects the appropriate contractual values, sets up the compliant configuration and carries out the prescribed series of measurements in full. Before that there is neither a confirmed line fault nor an automatically owed discount. The proof route is intended precisely to make the specific connection comparable with the agreed performance.
The protocol is the starting point for the next decision
After completion the measurement protocol contains the essential results and measurement details. It is submitted to the provider for assertion. [BNetzHand][BNetzTempo] An underperformance recorded in the protocol does not automatically quantify the legally correct reduction amount. The Bundesnetzagentur expressly explains this separate clarification. [BNetzStoer]
§ 57 governs reduction and extraordinary termination including a corresponding application of the remedy rule. [TKG57] Therefore have the concrete response together with the necessary remedy options clarified after the proof. Unexamined reductions are not derived from a single low measurement result alone. The complete protocol and the provider's reply remain together with the case.