Slow Mobile Internet in Germany: How to Prove a Speed Shortfall and Reduce Your Bill in 2026

Slow mobile internet is no longer simply a matter of comparing a speed-test result with the number advertised by a mobile operator. Since 20 April 2026, consumers in Germany have had a formal measurement procedure for proving that a mobile internet connection performs significantly below the estimated maximum speed stated in the contract. The Bundesnetzagentur introduced specific rules for mobile connections and a dedicated measurement app that can produce evidence for a price-reduction claim or, where the conditions are met, extraordinary termination of the contract. The procedure is stricter than an ordinary speed test because mobile performance changes with location, signal conditions and network load. A customer therefore needs several valid measurements rather than one disappointing result. Understanding the thresholds, measurement conditions and claim process is important because a poorly prepared test campaign may fail to establish reduced performance even when everyday mobile internet feels consistently slow.

What Changed for Mobile Internet Customers in Germany in 2026

The legal basis for claiming a reduction because of inadequate internet performance already existed under Section 57 of the German Telecommunications Act, or Telekommunikationsgesetz (TKG). The practical difficulty was proving a significant, continuous or regularly recurring speed discrepancy on a mobile connection. Fixed-line customers had an established measurement procedure much earlier, but applying the same approach to mobile networks was difficult because a smartphone is used in different places and available capacity varies from one radio cell to another. Bundesnetzagentur Decision No. 35/2026 addressed this problem by defining when a mobile speed discrepancy is considered sufficiently serious for the official evidence procedure. The decision became effective on 20 April 2026, together with the dedicated Breitbandmessung Nachweisverfahren Mobilfunk app.

The 2026 procedure compares the speed measured on the customer’s device with the estimated maximum download and upload speeds agreed in the mobile contract. These figures should not be confused with a general advertising headline such as “up to 300 Mbit/s”. The relevant values are the estimated maximum rates specified for the actual tariff, which consumers can normally find in the product information sheet or contract summary. If the tariff is already included in the application’s database, it can be selected there. If it is missing, the customer can enter the contractual values manually. Correct tariff information matters because the application uses those figures as the starting point for determining whether the measured connection falls below the formal threshold.

Unlike the fixed-line procedure, mobile internet has different thresholds according to local household density. Germany is divided into squares measuring 300 by 300 metres. In an area with high household density, the relevant speed level is 25% of the agreed estimated maximum; in an area with medium density it is 15%; and in an area with low density it is 10%. For example, if a contract specifies an estimated maximum download speed of 300 Mbit/s, the respective comparison levels would be 75 Mbit/s, 45 Mbit/s or 30 Mbit/s. These percentages determine whether a formal speed discrepancy can be established. They do not replace the speed stated in the contract and should not be interpreted as new guaranteed tariff speeds.

When Slow Speed Counts as Non-Compliant Performance

The standard measurement campaign allows up to 30 valid measurements across a maximum of five measurement days, with no more than six measurements on each day. A significant discrepancy exists if the applicable speed level is not reached at least once on at least three of the five measurement days in the download and/or upload direction. This is a demanding test. A connection that is slow for several measurements but reaches the relevant threshold once on enough measurement days may therefore fail to produce formal evidence of reduced performance. The system is designed to identify recurring serious underperformance rather than every temporary reduction caused by ordinary variations in a mobile network.

A measurement day can finish before all six measurements have been completed if the applicable threshold has already been reached for both download and upload. In that situation, further tests on the same day cannot change the assessment that the required level was achieved. The opposite situation requires more evidence: for a day to count towards proving reduced performance, the relevant speed must remain below the threshold throughout the required measurements for download and/or upload. A whole campaign may also end early once its result can no longer change. In the clearest underperformance case, six unsuccessful measurements on each of three days can therefore provide enough evidence after 18 valid measurements rather than requiring all 30.

This distinction explains why ordinary screenshots from commercial speed tests are not equivalent to the official 2026 evidence procedure. A single result showing 20 Mbit/s on a tariff advertised at several hundred Mbit/s may demonstrate that the connection was slow at that moment, but it does not satisfy the Bundesnetzagentur measurement rules by itself. The same applies to individual tests made with the general Mobilfunk-Check app. Consumers who intend to rely on Section 57 TKG should use the separate Breitbandmessung Nachweisverfahren Mobilfunk app. It records the campaign under controlled conditions and, where reduced performance is established, creates the measurement report intended for use with the provider.

How to Run a Valid Mobile Speed Measurement Campaign

Preparation should start with the contract rather than the phone. The customer needs the exact mobile tariff and its agreed estimated maximum download and upload rates. These figures may appear in the product information sheet, contract summary, customer account area or correspondence from the operator. It is worth checking that the tariff selected in the measurement app matches the current contract, especially after a tariff change or renewal. The measurement is based on contractual figures, so entering an old speed limit or choosing a similarly named but different tariff can make the resulting comparison unreliable. The dedicated app is available for supported Android and iOS devices and guides the user through the required campaign.

Measurements must also reflect suitable radio conditions. The Bundesnetzagentur procedure requires testing outdoors rather than inside a building or vehicle because walls, coated windows and vehicle bodies can weaken the mobile signal. The phone should remain at a fixed location while the test is running. The application checks movement and can reject measurements if movement exceeds the permitted level. Accurate location information is essential because the app must identify the relevant 300-by-300-metre household-density square. It also checks whether location accuracy is adequate. The connection must use broadband mobile technology of at least 4G, and a measurement may be rejected if the device drops to a lower mobile standard during the test.

The phone itself should not create an artificial bottleneck. A protective case should be removed, battery-saving mode should be switched off and the device should not be providing a hotspot. VPN connections and other traffic that could divert or consume bandwidth should be disabled, and no voice call should run during the measurement. On a dual-SIM phone, additional active mobile connections need to be deactivated so that the tested SIM is the only active mobile connection. The customer must also have enough unused data allowance; testing after the tariff has already been throttled for exhausting its monthly allowance does not test the normal contractual rate. Each measurement is started manually. Tests generally need at least five minutes between them, while at least three hours must separate the third and fourth measurements of a measurement day. The whole campaign must be completed within 14 calendar days after it starts.

Mistakes That Can Weaken or Invalidate the Evidence

One of the easiest mistakes is measuring under conditions that the procedure is specifically designed to exclude. A test made while travelling on a train, sitting inside a car or standing deep inside a building can produce a very low result, but the poor speed may be caused partly by shielding or movement rather than network capacity. The app therefore monitors factors such as movement, network technology and location accuracy. Location accuracy generally needs to remain within 30 metres for the measurement to be accepted. The application can also reject a test if the device changes from 4G to a lower network technology or if its operating system reports serious heat-related performance throttling. These checks may seem inconvenient, but they make the final report more useful when the provider examines the evidence.

Another common error is treating every speed test as legally equivalent. The general Mobilfunk-Check service remains useful for checking local speed or recording network availability, but individual tests from it are not the formal measurement campaign for a Section 57 claim. The dedicated Nachweisverfahren Mobilfunk app is the relevant tool. Customers should also avoid testing after their included high-speed data has been consumed, while international roaming is active, or while background downloads, cloud synchronisation, video streaming or software updates are using the same connection. A technically older phone may also limit achievable speed. The Bundesnetzagentur does not simply exclude every older model, but device information is recorded in the measurement report and can become relevant if the operator argues that the handset itself restricted performance.

It is useful to keep the contract summary and product information sheet alongside the final evidence. If reduced performance is established, the application generates a signed PDF measurement report containing the main campaign results and technical details of the individual measurements. If the connection is assessed as compliant under the formal procedure, such a reduced-performance report is not provided. Consumers should therefore save the successful report promptly together with the tariff information that shows the estimated maximum speeds used in the comparison. These records make it easier to show that the measurement campaign relates to the correct SIM, tariff and contractual speed rather than to an unrelated test performed under different conditions.

How to Request a Lower Price or End the Mobile Contract

Once the measurement campaign establishes reduced performance, the next step is to contact the mobile provider directly. The Bundesnetzagentur recommends presenting the measurement report while it is still recent, normally within four weeks after completion of the campaign. A written claim should identify the contract, explain that the official mobile measurement procedure has established non-compliant performance and state that the customer is asserting rights under Section 57(4) TKG. Keeping the correspondence in writing is useful because it creates a record of the claim, the date on which it was submitted and the provider’s response. The Bundesnetzagentur supplies the evidence mechanism, but it does not itself impose an individual bill reduction on the operator.

The amount of the reduction requires particular care. Section 57 TKG states that the contractually agreed charge is to be reduced in the proportion in which actual performance differs from contractual performance. However, the legislation does not provide a complete formula for every mobile tariff, and the official measurement report does not automatically calculate a euro amount. The Bundesnetzagentur states that the appropriate reduction may depend on the circumstances of the individual case, including the extent to which use is affected. The regional 25%, 15% and 10% measurement levels should therefore not be converted directly into discount percentages. They decide whether the formal evidence threshold has been crossed; they do not mean, for example, that a 75% measurement deduction automatically produces a 75% reduction in the monthly bill. The specific amount should be clarified with the provider.

If reduced performance has been established, the statutory right to a reduction continues until the provider demonstrates that it is again delivering the contractually required service. A customer whose main aim is to keep the contract may therefore ask the operator to correct the problem and adjust the charge while the shortfall remains. If the provider cannot remedy the reduced performance, extraordinary termination without observing the normal notice period may also be available under Section 57 TKG. Before relying on this option, the provider should generally be given an appropriate opportunity to remedy the problem. This is especially important where the dispute may later need formal settlement, because the customer should be able to show both the official measurement evidence and a reasonable attempt to resolve the issue directly.

What to Do If the Mobile Provider Rejects the Claim

A rejection does not make the official measurement report meaningless. The first practical step is to ask the provider to explain its position in writing. If it questions the tariff values, the customer can provide the contract summary or product information sheet. If it claims that the handset or measurement conditions affected the results, the report contains technical information that can help establish what happened during the campaign. It is sensible to retain the original signed PDF rather than only screenshots of selected pages, together with correspondence, bills and any response from the provider. This creates a clear record of the disagreement and reduces the risk that essential information is lost if the dispute continues for several weeks.

If direct discussions do not resolve the dispute, consumers can apply to the Bundesnetzagentur’s Schlichtungsstelle Telekommunikation for an out-of-court settlement procedure. An important condition is that the customer must normally have attempted to reach an agreement with the provider first. The mediation body acts as a neutral intermediary rather than automatically deciding that either side is correct, and participation does not prevent the matter from ultimately reaching a civil court if no agreement is reached. The Bundesnetzagentur itself does not enforce an individual price reduction or extraordinary termination. Its measurement rules and report provide the factual basis on which the customer can assert those rights against the provider.

There is also an important boundary to the 2026 mobile procedure. The Nachweisverfahren Mobilfunk app described here is intended for genuinely mobile internet access used on devices such as smartphones and mobile-enabled tablets. The Bundesnetzagentur’s 2026 guidance excludes mobile-network products used as stationary fixed-line replacements from this particular app-based procedure. Customers using a 4G or 5G connection permanently as home internet should therefore check which evidence procedure applies to their type of access rather than assuming that the smartphone campaign can be transferred directly to it. For ordinary mobile contracts, however, the rules effective since April 2026 finally provide a defined route from repeated poor speed to documented evidence: verify the contractual figures, complete the official measurement campaign correctly, keep the signed report and use it when requesting a price reduction or another contractual remedy.