The Truth About 'Unlimited' eSIM Plans — What Is FUP?
Not All "Unlimited" Plans Are Created Equal
When searching for eSIM plans for your trip abroad, you'll see "unlimited data" everywhere. It sounds like you can use data worry-free, right? But reality often tells a different story.
"I bought an unlimited plan, so why is it so slow?"
Most "unlimited" eSIM plans come with hidden conditions. The key concept behind this is FUP — Fair Usage Policy.
This guide breaks down what unlimited really means, the types of unlimited plans, and how to pick the right one.
What Is FUP (Fair Usage Policy)?
FUP stands for Fair Usage Policy — a rule set by carriers that essentially says: "You get high-speed data up to a certain amount, then we slow you down."
Why Does FUP Exist?
Network bandwidth is a shared, finite resource. If everyone used unlimited high-speed data simultaneously, the network would collapse. FUP helps carriers:
- Maintain network quality — prevent heavy users from hogging bandwidth
- Keep prices reasonable — truly unlimited high-speed would be very expensive
- Protect all users' experience — ensure stable service for everyone
FUP is essentially how carriers can advertise "unlimited" while keeping operations sustainable.
3 Types of "Unlimited" eSIM Plans
Type 1: Throttled After a Data Cap (Most Common)
This is the most common type by far.
- You get a set amount of high-speed data (4G LTE/5G)
- After using it up, speed drops dramatically to 128kbps–512kbps
- Data itself continues (hence "unlimited")
Examples:
- "5GB high-speed + unlimited at 128kbps after"
- "10GB 4G LTE then 256kbps unlimited"
This type accounts for over 80% of "unlimited" eSIM plans. The 128kbps throttle is essentially 2G-era speed.
Type 2: Daily Cap Unlimited
A fixed amount of high-speed data resets daily.
- Daily allotments like 500MB, 1GB, or 2GB of high-speed
- Exceeding the daily cap means throttled speed for the rest of that day
- Resets at midnight (local time)
Examples:
- "1GB high-speed daily, 128kbps after daily limit"
- "Daily 2GB 4G LTE + unlimited throttled"
Very common for Japan travel eSIMs. Works well if your daily usage is predictable, but can be frustrating if you use lots of data in one session.
Type 3: Top-Up After Depletion
Buy additional data manually or automatically after the base allowance runs out.
- Base data: 5GB, 10GB, etc.
- Purchase additional packages via the provider's app
- Some offer auto top-up
Examples:
- "10GB base + additional 1GB packs available"
- "Auto top-up: $3 per 1GB when enabled"
Not truly "unlimited," but some providers market it as such since data never fully cuts off. Watch out for unexpected charges with auto top-up.
Does "Truly Unlimited" Exist?
Some premium plans claim "no speed limits, truly unlimited." But genuinely unlimited high-speed data is extremely rare. Here's why:
Hidden Restrictions
Even "fully unlimited" plans often have:
- Speed reduction after 2–3GB/day — not explicitly stated, but buried in terms like "speeds may be reduced during network congestion"
- Tethering/hotspot limits — phone data may be unlimited, but sharing via hotspot has a separate cap or is blocked entirely
- App restrictions — VPN, P2P (torrents), and other bandwidth-heavy services may be blocked
- "Network management" clauses — broad terms allowing the carrier to throttle as needed
Why True Unlimited Is Nearly Impossible
eSIM providers operate as MVNOs, renting network capacity from local carriers. Local carriers have no incentive to give foreign travelers the same unlimited access as domestic subscribers, so FUP is built into wholesale agreements.
If you truly want high-speed unlimited with no restrictions, expect to pay a significant premium — often 2–3x the price of standard "unlimited" plans.
What Can You Actually Do at 128kbps?
Works Fine
| Service | Experience |
|---|---|
| Text messaging (KakaoTalk, WhatsApp, iMessage) | Slightly delayed but functional |
| Email (text only) | Attachments take a long time |
Slow but Usable
| Service | Experience |
|---|---|
| Google Maps / navigation | 10–20 second load times; use offline maps |
| Text-heavy web browsing | Image-heavy pages are very frustrating |
| Translation apps | Text translation OK; photo translation slow |
Practically Impossible
| Service | Experience |
|---|---|
| YouTube / Netflix | Constant buffering |
| Instagram feed | Photos/Reels barely load |
| Video calls | Severe quality loss and disconnections |
| App downloads/updates | Essentially won't complete |
| Cloud photo uploads | Endless upload |
Bottom line: At 128kbps, only text-based communication works reliably. If you plan to use maps, social media, or streaming while traveling, choose a plan with generous high-speed data.
How to Choose Wisely on esimoa
1. Estimate Your Daily Usage
- Light use (maps, messaging, occasional search): 500MB–1GB/day
- Moderate use (social media, photo uploads, browsing): 1–2GB/day
- Heavy use (video, tethering, active social media): 2–3GB+/day
For a 5-day trip, moderate users need 5–10GB; heavy users should aim for 10–15GB+.
2. Look Past the "Unlimited" Label
Focus on actual high-speed data, not the marketing label:
- "Unlimited (3GB high-speed)" = effectively a 3GB plan
- "Unlimited (10GB high-speed)" = effectively a 10GB plan
- "1GB/day unlimited" = 5GB total high-speed for a 5-day trip
3. Check FUP Conditions
The throttle speed varies:
- 128kbps: messaging only (most common)
- 256kbps: basic text browsing possible
- 512kbps–1Mbps: low-quality maps and basic web browsing work
4. Compare Price Per GB
Convert unlimited plans to cost per GB of high-speed data:
- Plan A: Unlimited (5GB high-speed) at $11 → $2.20/GB
- Plan B: Unlimited (10GB high-speed) at $16 → $1.60/GB
Plan B offers better value for high-speed data.
5. Match Your Travel Style
| Travel Style | Recommendation |
|---|---|
| Accommodation has good Wi-Fi | Small plan (3–5GB) may suffice |
| Out and about all day | Daily cap plan or large plan (10GB+) |
| Tethering to multiple devices | Verify tethering is allowed |
| Long trip (2+ weeks) | Plan with top-up option |
| Heavy SNS/video use | Generous high-speed data is a must |
Summary
| Topic | Key Takeaway |
|---|---|
| What "unlimited" really means | Usually has a high-speed cap, then throttled to 128kbps |
| What FUP is | Fair Usage Policy — speed limits after a set data amount |
| True unlimited | Extremely rare; hidden restrictions almost always apply |
| Life at 128kbps | Messaging works; maps/SNS/video essentially don't |
| Smart choice | Compare by high-speed data amount and FUP conditions, not the "unlimited" label |
Don't be fooled by the word "unlimited." The real question is always: how much high-speed data do I actually get?
Related guides: