Bufferbloat grade
Waiting for a result
The largest rise in loaded latency determines the grade.
What does this grade mean?Use a Bufferbloat Test to Understand Why Fast Broadband Can Still Lag Under Load
Fast full fibre can still lag when uploads, downloads, Wi-Fi traffic or router queues fill up. This live test compares quiet latency with loaded latency on FTTP, cable, FTTC, Wi-Fi and 5G connections.
- Fibre bufferbloat
- Loaded latency
- Gaming ping
- Video calls
Run the Fibre Bufferbloat Test
Test whether your fibre connection stays responsive while busy. LinkSpeed compares idle latency with download and upload latency to detect bufferbloat caused by router queues, Wi‑Fi or broadband congestion.
How are you testing today?
Choose the connection used by this device. The measurement method stays the same; this only tailors the diagnosis.
Before You Start
Prepare for a useful result
- Pause downloads and backups.
- Disconnect VPNs and proxies.
- Compare Wi-Fi with Ethernet.
Test in progress
Preparing the test
Checking browser support and selecting the nearest available route.
Current ping—ms
Downloaded0MB
Uploaded0MB
Test could not finish
The live test was interrupted
Check the connection and try again.
Your live results
Bufferbloat test results
See the headline grade first, then compare unloaded latency with download and upload load before following the recommended next step.
Unloaded latency
—ms Baseline median with no active loadDownload active
—ms Added latency while downloading
Waiting for result
Upload active
—ms Added latency while uploading
Waiting for result
Measured speed
↓—Mbps
↑—Mbps
Cloudflare download and upload route
Connection suitability under load
What should remain usable while your line is busy?
✓ Likely suitable in this test
× Potential issue detected
Web browsing
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Audio calls
—
4K streaming
—
Video conferencing
—
Low-latency gaming
—
These estimates use this browser test only. A game server, video-call platform or streaming route may behave differently.
View detailed latency, jitter and percentile measurements Median, middle 50%, measured range and browser samples
Latency distributions
How stable was each phase?
Each strip shows the median, middle 50%, full measured range and individual browser latency samples.
Unloaded—
Download active—
Upload active—
Speed and accuracy note: results measure browser requests to Cloudflare, not ICMP ping to a game server or workplace. Browser handling, VPNs, security software, Wi‑Fi and internet routing can affect throughput and latency. Compare Ethernet and Wi‑Fi results and repeat the test at different times. The rise in latency under load is the main bufferbloat indicator.
What Is Bufferbloat?
Bufferbloat is excessive delay caused when a router or network link holds too much traffic in a queue. The connection can still show a fast download speed, but gaming, video calls and browsing become slow or erratic whenever downloads, uploads or backups fill that queue.
Understand the score
Bufferbloat Grade Bands
The worst median increase from the download or upload phase sets the grade. Jitter and 95th-percentile spikes are shown separately in the detailed results.
A+0–5 msExceptional
A>5–25 msGood
B>25–60 msMild delay
C>60–100 msNoticeable
D>100–150 msHigh delay
F>150 msSevere
FTTP and gigabit connections
Fibre Bufferbloat Test: How to Run It on Full Fibre Broadband
Full fibre broadband can still suffer from bufferbloat. FTTP removes the copper-line bottleneck, but queues can still build in the router, Wi-Fi connection, Ethernet interface or upload path. Run the test over Ethernet first, then repeat over Wi-Fi to identify where the additional delay begins.
Why Does My FTTP Broadband Lag When Gaming?
Full fibre can deliver excellent quiet ping but still lag when uploads, downloads or Wi-Fi traffic fill a queue. Compare the upload and download loaded-latency results, then repeat over Ethernet. A good wired result points to Wi-Fi; a poor wired result points to router queue management or the broadband path.
How This Test Works
Compare quiet latency with latency under load
The browser records a quiet baseline, loads the download and upload paths, then compares median delay and high-percentile spikes. The largest increase determines the grade.
IdleDownloadUploadGrade
Short Video Guide
See How to Test for Bufferbloat
Watch the short LinkSpeed guide to see what loaded latency means, how the test works and what to check if your ping rises while the connection is busy.
What to Fix When the Test Finds High Loaded Latency
Retest over Ethernet
If the wired grade is good but Wi-Fi is poor, fix wireless interference, signal strength or access-point placement first.
Enable SQM or QoS
CAKE and FQ-CoDel are designed to keep queueing delay controlled when the line is busy.
How to Fix Bufferbloat
Control upload saturation
Cloud backup, security cameras, file sync and livestreaming can fill a slower upstream path quickly.
Shape below line rate
On supported routers, set shaping slightly below the measured maximum so the managed queue remains the bottleneck.
Hardware route
Choose hardware only after the wired comparison
A new router or mesh system is most useful when the test identifies where the delay begins. Do not replace working hardware solely because one Wi-Fi test produced a poor grade.
The linked buying guide may contain Amazon affiliate links. As an Amazon Associate, LinkSpeed earns from qualifying purchases.
Focused answers
Bufferbloat Test FAQs
Use these answers to understand the test, verify a poor result and choose the correct fix.
What is bufferbloat?
Bufferbloat is excessive delay caused when a router, Wi-Fi link, modem or broadband bottleneck stores too much traffic in a queue. The connection may still look fast, but games, calls and browsing become slow when downloads or uploads fill that queue. For a deeper explanation, read What Is Bufferbloat?
How does the LinkSpeed bufferbloat test work?
The browser measures quiet latency, then continues sampling while Cloudflare download and upload traffic loads the connection. It compares the median increase, jitter and high-percentile spikes before assigning a grade based on the worst loaded phase.
What is a good bufferbloat grade?
A+ or A means loaded latency stayed close to the quiet baseline. B usually indicates mild delay. C, D or F means the connection becomes increasingly unresponsive under load and should be verified over Ethernet before changing settings or hardware.
Can full fibre broadband still have bufferbloat?
Yes. FTTP removes the copper access-line bottleneck, but queues can still build in the router, Wi-Fi link, Ethernet interface or upload path. Compare Ethernet and Wi-Fi results to identify where the additional delay begins.
Is a fibre bufferbloat test worth running on full fibre broadband?
Yes. A full fibre line can have excellent quiet latency but still suffer high loaded latency when uploads, downloads, Wi-Fi or router queues become saturated. Test over Ethernet first, then repeat over Wi-Fi.
Should I run the test over Wi-Fi or Ethernet?
Run both when possible. Ethernet gives the clearest view of the router and broadband path, while Wi-Fi reflects the experience of the device you use. A poor Wi-Fi grade with a good wired grade points towards wireless conditions rather than line bufferbloat.
How do I fix a poor bufferbloat result?
Repeat the test over Ethernet with other traffic paused. If the wired result remains poor, enable effective SQM or QoS, use CAKE or FQ-CoDel where supported, and shape upload and download slightly below the stable measured rates.
Why is the measured speed lower than another speed test?
This test prioritises continuous latency sampling while generating load rather than chasing the highest possible throughput. Browser limits, VPNs, security software, Wi-Fi and routing can affect speed, so the rise in latency under load is the main result.