Throttling occurs when data transfer is capped at a specific speed. Often, these caps apply to all data usage. For example, as of April 2019:
- Mint Mobile subscribers who’ve used up their allotted high-speed data have speeds throttled to a maximum of 128kbps.
- Visible generally caps data speeds at 5 megabits per second (Mbps)
In my experience, carriers are usually transparent about (a) the existence of throttling on data speeds and (b) the speeds that subscribers will be capped at.
Carriers may also throttle specific applications or types of traffic. This sort of targeted throttling often affects video streaming (see this Bloomberg article for more details).
Prioritization can affect the quality of service that subscribers receive when networks are congested. Rather than treating all users of a congested network equally, network operators generally prioritize some users’ activities over other users’ activities.
The conventional wisdom is that networks tend to give the highest priority to their most valuable customers. In other words, network operators’ post-paid customers generally receive the highest priority, followed by their pre-paid customers, with subscribers to mobile virtual network operators (carriers that use networks owned by other companies) receiving the lowest priority. However, that assessment is pretty high-level and may miss some nuances. Unfortunately, I’ve found that carriers don’t usually share many details about their prioritization procedures.
Prioritization will sometimes occur within a single class of customers. For example, sometimes post-paid customers that use excessive amounts of data will have their network access deprioritized. Better prioritization may sometimes be offered as a benefit of more expensive service options. Here are a few examples of prioritization affecting those that subscribe to Verizon’s post-paid unlimited plans:
- GoUnlimited: “In times of congestion, your data may be temporarily slower than other traffic.”
- BeyondUnlimited: “After 22 GB/line, in times of congestion, your data may be temporarily slower than other traffic.”
- AboveUnlimited: “After 75 GB/line, in times of congestion, your data may be temporarily slower than other traffic.”
Unlike throttling, prioritization is not going to affect an individual’s wireless experience when a network is not congested.
- “When your data is reduced, it will be reduced to 128 kpbs.”
From a Mint Mobile support response on the Mint Mobile community forum (archived here).
- “We’re built for life on the go, so instead of giving you extra speed you don’t need (and making you pay for it), you get unlimited data at speeds up to 5 Mbps.”
From Visible’s FAQ as of 4/24/2019 (archived here).
- In my experience, carriers often mention that deprioritization is a possibility, but they rarely share enough details for consumers to really assess how significant an effect deprioritization is liable to have on their experience. As of April 2019, I’ve never seen a third-party company try to make a rigorous, empirical assessment of differences in prioritization between services.
- These examples come from Verizon’s unlimited plans web page as of 4/26/2019.