Maybe you’ve experienced this situation before. Before traveling abroad, you buy a SIM card or rent a mobile WiFi device to stay connected. To make sure you don’t run out of data, you even choose an unlimited plan. But once you’re abroad, you suddenly notice that the internet speed becomes incredibly slow at times.

This makes you wonder: Isn’t my plan unlimited? Why is my speed being throttled?

Here’s the answer.

Fair Usage Policy / FUP

It’s not your data that’s being limited—it’s the speed. This is due to something called the Fair Usage Policy (FUP).

So, what exactly is the FUP?

First, it’s important to understand that when you’re online, many others are also using the internet at the same time, and some might even be using the same network provided by your internet service provider.

Let’s use an example to make this clearer.

Imagine you’re on a treadmill with someone else. When both of you are running at a normal pace, everything is fine, and you can enjoy your workout. But if the other person starts running erratically, taking up most of the treadmill space, you’re left with very little room to run—or none at all.

The internet works similarly. If someone uses a large amount of data in a short period, it can slow down the network for others. To prevent this, many countries enforce a Fair Usage Policy, which limits the speed of users who consume excessive data in a short time. This helps ensure a smoother internet experience for everyone.

Even if you order a SIM card or WiFi device from a country without such a policy, it may still be subject to the FUP.

What Triggers a Speed Limit?

Our partner, CDJapan Rental, often receives questions like:

“I need to update my phone’s system today—will that trigger a speed limit?”
“I’ve watched a lot of YouTube videos over the past few days—will that cause a speed limit?”
“Why did I start experiencing a speed limit today when there wasn’t one two days ago?”
“Why is my speed limited?”
There’s no clear rule about how much data usage will result in a speed limit. The Fair Usage Policy is designed to protect users who are using the network normally. It only limits the speed of those who consume so much data that it could disrupt others. If there aren’t many users online, heavy data usage might not cause issues, such as during late nights or early mornings, when you can download as much as you want within your data allowance. However, during peak times like holidays or evenings, downloading large files or streaming HD videos could be seen as “disrupting other users” and may lead to a speed limit.

How to Avoid Speed Limits

To avoid getting your speed throttled, consider these tips:

• Avoid heavy data usage during peak hours.
• Turn off automatic app updates.
• Disable automatic cloud syncing for photos, emails, etc.
• Turn off auto-play videos on social media apps.
• Use free WiFi whenever possible.

Some rental WiFi providers specify that if you use more than a certain amount of data within a short period, your speed will be limited. Be mindful not to exceed these limits during continuous usage.

For More Data

Alternatively, you can opt for a rental WiFi plan that offers ample data.

Check out CDJapan Rental’s WiFi devices—they offer unlimited data WiFi.

Stay Connected in Japan!