Plex Buffering on NAS: How to Fix It

Plex buffering on a NAS is almost always fixable without buying new hardware. Enable direct play for supported clients, cap remote streaming quality to match your upload speed, and check your network for wireless interference or congestion. If the NAS CPU is genuinely the bottleneck, a model with Intel Quick Sync hardware transcoding resolves it permanently. Work through these fixes in order before concluding the hardware is the problem.

Why Plex Buffers on a NAS

Plex buffers when the server cannot deliver video data to your client fast enough. On a NAS, this breaks down into three causes: the NAS is transcoding a file it doesn't need to (and the CPU can't keep up), the network between your NAS and your device is too slow, or your internet upload speed is the bottleneck for remote streams. Each cause has a different fix. Which is why jumping straight to hardware is usually the wrong move.

Transcoding is the process of converting a video file from one format or resolution into another that your playback device can understand. Think of it as a live translator working in real time. Direct play is the opposite: the file plays exactly as stored, with no conversion needed. Direct play requires almost no CPU resources; transcoding can max out an entry-level NAS processor with a single 1080p stream. Eliminating unnecessary transcoding is almost always the first fix.

Fix 1: Enable Direct Play and Direct Stream

In the Plex web interface, go to Settings, then Quality (under the player, not the server). Set Remote and Local quality to "Original" or "Maximum," and ensure both "Allow Direct Play" and "Allow Direct Stream" are enabled. Direct play sends the file to your device unchanged; direct stream sends the original video with a re-packaged audio track. Both are far less demanding than transcoding. If your client supports the file format, Plex will use direct play automatically at these settings.

If your files are HEVC or AV1 and your playback device doesn't support them natively, Plex must transcode. Smart TVs from 2018 or later and Fire TV 4K devices handle HEVC direct play; older TVs and Fire TV Sticks without 4K support often cannot. The long-term solution here is either to have your content encoded in H.264 (universally compatible) or use a client with broader codec support like an Apple TV 4K or NVIDIA Shield.

Fix 2: Reduce Remote Streaming Quality

Remote buffering. Buffering when you're outside your home network. Is almost always caused by internet upload speed rather than NAS hardware. In the Plex app on your remote device, go to Settings, then Quality, and under Remote Streams set the quality to 4 Mbps or 8 Mbps. This forces Plex to transcode the video down to a manageable bitrate before sending it over your internet connection. A standard NBN 50 plan delivers roughly 18-20 Mbps upload. Enough for one or two capped remote streams, but not for original-quality 4K.

Fix 3: Check Your Network

For local network buffering (streaming within your home), the most common cause is Wi-Fi interference or a weak wireless signal. A 2.4 GHz Wi-Fi connection in a congested apartment building shares spectrum with neighbours' networks and can drop below the bandwidth Plex needs mid-stream. Switch your streaming device to the 5 GHz band if available, or better yet, connect either your NAS or your streaming device (or both) to your router via Ethernet. A wired connection eliminates interference and typically delivers 100-1000 Mbps. Far more than any Plex stream requires.

If wiring is not practical, a powerline adaptor or MoCA adaptor can carry Ethernet over existing power or coaxial cables in your home. These are more reliable than Wi-Fi for media streaming and typically cost $50-150 for a pair. For the NAS specifically. If your router is nearby. A single Ethernet run solves the NAS side permanently regardless of what your client device uses.

Fix 4: Check NAS CPU Load During Playback

If direct play is enabled but buffering continues on local streams, check the NAS CPU load while video is playing. In Synology DSM, open Resource Monitor. In QNAP QTS, open System Resource Monitor from the main menu. In Asustor ADM, open the Resource Monitor from System Preferences. A CPU sitting at 80-100% during playback confirms the NAS is transcoding and struggling. If direct play were working, CPU usage during Plex playback would be below 20%.

High CPU during playback with direct play enabled usually means the format is genuinely unsupported by your client. High CPU even at idle (before Plex starts) suggests background services are competing for resources. Check whether any running apps. Download clients, backup jobs, surveillance station, or cloud sync. Are consuming CPU. Suspending them while streaming can restore headroom on entry-level NAS models with ARM processors and 2-4 GB RAM.

Fix 5: Close Background Apps and Services

NAS devices run multiple services simultaneously, and some background tasks compete directly with Plex for CPU and RAM. Scheduled backup tasks (particularly cloud sync or Time Machine backups) are common culprits. They often run at night but can overlap with evening streaming sessions. Anti-virus scans, thumbnail generation, and download clients all consume meaningful CPU on entry-level hardware. Reschedule these tasks to run between 2am and 6am when the NAS is otherwise idle.

Docker containers and virtual machines running on the same NAS compound the problem significantly. If your NAS runs Portainer, Home Assistant, or other containers, check their CPU and RAM consumption in the container manager. A single misbehaving container can consume enough RAM to trigger memory swapping, which degrades Plex performance even when the Plex process itself is not the bottleneck.

Fix 6: Upgrade to a NAS with Hardware Transcoding

If you have worked through fixes 1-5 and still experience buffering when the NAS must transcode (HEVC files, clients that don't support direct play, multiple simultaneous streams), the NAS hardware is the bottleneck. ARM-based NAS devices. QNAP TS-233, Asustor AS3302T, many Synology J-series and Value-series models. Cannot transcode in real time regardless of configuration. They need to be replaced with a model that has Intel Quick Sync Video hardware transcoding support.

Prices last verified: 7 June 2026. Always check retailer before purchasing.

Hardware transcoding requires a Plex Pass subscription, but once enabled it offloads video conversion from the main CPU to Intel's dedicated Quick Sync Video encoder. The Synology DS225+ ($529) is the most affordable entry point for hardware transcoding in a 2-bay NAS; the QNAP TS-462 ($899) offers the same capability in a 4-bay form factor. For a deeper breakdown of models by tier and use case, see the Best NAS for Plex Australia guide.

Why does Plex buffer on a fast NAS with a good network?

The most common reason is transcoding. Even a fast NAS will buffer if it's converting video in software on a slow ARM CPU. Check the Playback Info while streaming to confirm whether Plex is transcoding or direct playing. If it's transcoding, investigate why: the client likely doesn't support the file format natively, or quality settings are forcing a lower bitrate than the original file.

Does Plex Pass fix buffering?

Plex Pass unlocks hardware transcoding on NAS models with Intel Quick Sync Video, which eliminates CPU-bound buffering on compatible hardware. It does not fix network-related buffering, NBN upload speed limits, or buffering caused by ARM processors that lack hardware transcoding support. If your NAS uses an Intel CPU, Plex Pass plus enabling hardware transcoding in Settings will usually resolve transcoding-related buffering.

Plex is direct playing but still buffering. Why?

Direct play with local buffering is almost always a network issue. Check that your streaming device is on the 5 GHz Wi-Fi band or, better yet, wired via Ethernet. A Wi-Fi connection that looks like it has signal can still have low effective throughput due to interference or distance from the router. Run a speed test from your streaming device to confirm actual bandwidth. If the network checks out, check NAS disk health. A failing drive will throttle read speeds.

How much internet upload speed do I need for Plex remote access?

For a single remote 1080p stream: at least 8-10 Mbps upload, ideally 20 Mbps. For 4K direct play: 40-80 Mbps upload. For 4K with transcoding at reduced quality: 8-20 Mbps. Australian NBN 25 plans top out at around 5 Mbps upload, which is insufficient for most remote streaming. NBN 100/20 delivers 20 Mbps upload and handles one or two capped 1080p streams reliably. NBN 250/25 or higher is needed for 4K remote direct play.

Can I run Plex on an ARM NAS at all?

Yes, for direct-play libraries. ARM NAS devices (QNAP TS-233, Asustor AS3302T, many Synology entry models) serve Plex well when your clients support the file format natively. H.264 MKV files on a Fire TV 4K, for example, will direct play without issue. Problems arise when transcoding is needed: ARM processors cannot transcode in real time, and Plex will buffer or fail on those streams. If your library is mixed format or your clients vary, an Intel NAS is the reliable choice.

What is CGNAT and how does it cause Plex buffering?

CGNAT (Carrier-Grade NAT) is a configuration some Australian NBN providers use where multiple customers share the same public IP address. Under CGNAT, your router doesn't have a publicly accessible IP, so Plex cannot establish a direct connection to your server from outside your home. Instead, all traffic routes through Plex's relay servers, which adds latency and reduces throughput. Contact your ISP to check if you're on CGNAT. Many will assign a dedicated public IP on request, often at no charge.