Internet Connection Speed Comparison 2026 Edition | How to Choose by IPv6 Support and Measured Values

At 9 p.m., the video suddenly stops. The same connection works fine during the day, so why does it slow down at night? Many people first suspect their plan, but when you compare publicly available information, the cause is often "IPv4 or IPv6" and "congestion during evening hours." Here, we outline the order of checks for choosing a fast connection.

結論：まずIPv6(IPoE)対応を確認し、実測は「自動」で行う

結論：速度の差を生みやすいのは、IPv4でNTTの網終端装置を通る経路か、IPv6(IPoE)で混雑を避ける経路かです。夜間の混雑を避けたいなら、IPv6(IPoE)に対応した回線を選ぶのが第一歩になります。実測では、BNRスピードテストが案内するとおり、速い回線では測定サーバの上限に当たることがあるため、固定モードではなく「自動」で測るのが適切です。

IPv4とIPv6、どちらが遅くなりやすいのか

IPv4の通信は、多くの場合NTTの網終端装置を経由します。この装置に利用者が集中する夜間は、速度が落ちやすいと説明されています。一方、IPv6(IPoE)は網終端装置を通らずに直接インターネットへ接続する方式で、混雑を避けられる仕組みです。

夜間に差が出やすい理由

同じ光回線でも、経路が混むのは時間帯によります。昼はIPv4でも問題が出にくく、夜に差が開くのはこのためです。

「平均何Mbps速くなる」は条件付きで読む

ブログや解説記事には「平均で何Mbps上がった」という実測報告が多くあります。ただし、測定時間帯、プロバイダ、ルーターの対応状況で数値は大きく変わります。数字そのものより、どの条件で測ったかを確認してください。

実測値の取り方：誤差を減らす3つの手順

実測は、次の順で行うと比較しやすくなります。

1. 有線LANで測る。無線は電波状況の影響を受けやすいため、比較の基準には向きません。
2. 測定サイトは「自動」モードで実行する。固定モードは診断用で、速い回線では測定サーバの上限に当たることがあります。
3. 夜間と昼間の両方で測り、同じ時間帯どうしで比べる。

比較表の読み方

光回線の実測ランキングは、どう読めばよいか

みんそくデータを基にしたランキングでは、下り速度の平均で独自回線系の光回線が上位に並ぶ傾向が示されています。たとえば、kaisen-hikaku.netの集計では、NURO光の平均が588Mbpsとされています。ただし、これは集計条件つきの数値で、自分の住所や建物の設備で結果は変わります。

一方、ぼくの回線ガイドは、速い光回線を選ぶ条件として独自回線、IPv6 IPoE、プロバイダの混雑度の3つを挙げています。ランキングの順位だけで決めず、この3条件に自分の環境を当てはめるのが実用的です。

接続時間の差は小さいという報告もある

ゆうすけ氏のnote記事では、IPv6とIPv4の接続時間の差が約2.1%だったと報告されています。接続時間と通信速度は別の指標です。速さの改善を期待するなら、体感のスループットを測る必要があります。

回線選びのチェックリスト

• IPv6(IPoE)に対応しているか、ルーターも対応しているか
• 夜間の実測データが公開されているか、出典と集計期間が明記されているか
• 独自回線か、一般的な網を使う回線か
• 月額料金と初期費用、契約期間の縛りがあるか

Common Misconceptions

"Fiber is fast" is only half true. The type of network, IPv6 support, and peak-hour congestion all have to line up before you notice a real difference. Also, even if a speed test shows a high number, an old router will cap your speeds at a lower ceiling. Check the equipment standards as well.

Conclusion: If You Suspect Slowdowns at Night, Check IPv6 Support First

First, check IPv6 (IPoE) support, and then run speed tests in wired "automatic" mode at both midday and night. This gives you the most reliable basis for judgment. Choosing a connection based on this verification result leads to fewer mistakes than relying on the speeds listed in your contract plan.

Note

This article summarizes information published on the sites listed above. Prices and campaigns change frequently, so please check each provider's official website for the latest details.

Methodology: This article summarizes publicly available information from the sources listed below, as of 2026-10-17. The editorial team has not personally tested any of the connection services described. Affiliate disclosure: This article contains no affiliate links.

FAQ

Will switching to IPv6 (IPoE) always make my connection faster?

We can't say it always will. IPv4 is described as prone to congestion in the evening because it passes through a carrier-grade NAT (network termination device), whereas IPv6 (IPoE) is a method that connects directly and can avoid that congestion. However, it requires support from your router and contract, and the effect varies depending on the line and the time of day. Check by measuring speeds both during the day and at night.

Should I measure speed in fixed mode or automatic mode?

Automatic mode is the appropriate choice. BNR Speed Test explains that fixed mode is a diagnostic mode that does not use high-speed CDNs, and that on fast lines it may hit the upper limit of the test server. It is also explained that fixed mode results are not recorded in statistics.

Should I test over Wi-Fi or wired LAN?

Testing over a wired LAN is the basic approach. Wireless results depend on signal conditions and the device's location, so if you want to compare the speed of the line itself, a wired connection produces less error.

Can I trust rankings of measured fiber-optic line speeds?

They are useful if you check the aggregation conditions. Rankings based on Minsoku data show proprietary-network providers such as NURO Hikari at the top by average download speed. However, results vary by aggregation period, region, and measurement time of day, so it is important not to decide based on rankings alone.

Will switching to IPv6 also shorten connection time?

One report found that connection time was almost the same as IPv4, with a difference of about 2.1%. Connection time and communication speed are separate metrics, so to confirm a speed improvement, you need to measure throughput.

What should I check first when choosing a line?

Check whether IPv6 (IPoE) is supported, whether your router supports it, whether the line is a proprietary network, and the source and aggregation period of any measured data. Then compare the monthly fee, initial costs, and contract lock-in period to gather the information you need to decide. Prices change, so check each provider's official website for the latest information.

Sources & Verification

This article was fact-checked on 2026-10-17. Key claims:

• "IPv4 traffic passes through NTT's carrier-grade NAT (network termination device), so speeds tend to drop during evening congestion. IPv6 (IPoE) tends to avoid congestion through direct connections." — verified via https://ardent.jp/rentoffice-consultation-center/cloudpbx-info/ipv6-hikakul/ on 2026-10-17
• "The fixed mode is a diagnostic mode that does not use a high-speed CDN, and on fast lines the measurement server may become the limit. For the highest speed, measure in automatic mode." — verified via https://www.musen-lan.com/ipv4-ipv6-hikaku.html on 2026-10-17
• "A measured report found the connection times for IPv6 and IPv4 were nearly the same, with a difference of 2.1%." — verified via https://note.com/yusuke_webmarke/n/n460fb942863c on 2026-10-17
• "In a download speed ranking based on Minsoku data, NURO Hikari's average is 588Mbps." — verified via https://kaisen-hikaku.net/guide/speed-ranking/ on 2026-10-17
• "The conditions for a fast fiber line are listed as an independent network, IPv6 IPoE, and provider congestion level." — verified via https://internet-guide.jp/hayai-hikari-ranking/ on 2026-10-17