Once you’ve got a Usenet provider and an indexer (see the setup guide), the next decision is which downloader to run: SABnzbd or NZBGet. These are the two giants of the binaries world, and people argue about them like sports teams. Let me settle it for you with actual reasoning instead of tribal loyalty.
Short version: most people should use SABnzbd. NZBGet is only clearly better in two narrow situations. Here’s why — and at the end I’ll dig into the large-transfer stability question, because on modern UK fibre that’s often the deciding factor nobody mentions.
What They Both Do
Both SABnzbd and NZBGet do the same core job: take an NZB, connect to your provider over SSL, pull the articles, verify with PAR2, extract, and rename the finished file. Both integrate with Sonarr/Radarr and both support any provider you can find. On the fundamentals — speed, completion, SSL, automation — they’re functionally tied.
The real differences are in resource usage, maturity, and where you run them.
SABnzbd: The Safe Default
SABnzbd is the one most guides recommend and the one with the biggest community. It’s written in Python, mature, and relentlessly maintained.
Why you’ll like it:
- Most documented. Every Sonarr/Radarr/automation guide assumes SABnzbd. You’ll never be stuck with no tutorial.
- Best default setup UX. The browser UI is polished, the wizard configures your provider quickly, and it walks you through the first download.
- Easiest to debug. Big user base means almost any error you hit is already answered on its forum.
- Gentle concurrency defaults. It handles high connection counts reliably without crashing, which matters on gigabit fibre.
The downside: SABnzbd is heavier on RAM and CPU, especially for PAR2 repairs and post-processing on a busy library. On an old PC or a low-spec NAS it can feel sluggish. On modern hardware you won’t notice.
NZBGet: The Lightweight Option
NZBGet is written in C++ and is dramatically lighter on resources. On the right hardware it’s both faster and more efficient than SABnzbd.
Why you might use it:
- Minimal RAM/CPU. It’s the classic choice for a potato NAS, a Raspberry Pi, or any always-on box with limited RAM. It’ll saturate gigabit on hardware where SABnzbd chokes.
- Raw speed. On modern multi-core systems NZBGet can outperform SABnzbd slightly during heavy repair.
- Efficient post-processing. Uses far less juice while unpacking and repairing.
The real catch: NZBGet’s development effectively stalled. It hasn’t seen the level of active development SABnzbd has, recent releases are sparse, and some users have hit bugs that simply don’t get fixed. For a piece of software you’ll run unattended 24/7, “not actively maintained” is a genuine risk.
Large-Transfer Stability: The Decision Nobody Talks About
Here’s the section most comparisons skip, and it’s the one that bites hardest on modern UK fibre. “Which is faster” is the wrong question on a single download. The real question is which one stays stable when you run hundreds of gigabytes a week.
The PAR2/repair bottleneck
Both tools download fast — the difference shows up in verification and repair. On a modern release with 5–10% parity (see the PAR2 repair science section for why that budget is fixed), a repair is a CPU- and I/O-heavy Reed–Solomon decode across every byte of the file. When a repair stalls or fails, the fix routine is in fixing a failed repair.
- SABnzbd does this in Python via
par2cmdline. It’s reliable and predictable, but on a low-end CPU it makes the machine feel sluggish while a big download is finishing its repair. - NZBGet built verifier and repair into its C++ core and parallelises it well. On multi-core hardware it can chew through a repair noticeably faster, and with far less RAM than SABnzbd.
The catch: for that speed advantage to matter, the repair has to be the bottleneck — i.e. you’re on constrained hardware and your CPU is genuinely the limiting factor. On any half-decent modern machine, SABnzbd repairs fast enough that the difference is irrelevant.
Sustained throughput on gigabit
On a line that’s saturated for hours, the failure mode isn’t peak speed — it’s long-run stability: memory bloat over a multi-hour transfer, tempera spikes, and the client quietly backing off connections.
- SABnzbd’s Python overhead means it uses more RAM the longer and busier it runs, but it’s also the one with a huge installed base reporting the exact multi-hour/multi-day soak scenarios on every combination of hardware. That soak-testing is real-world insurance.
- NZBGet sips RAM and stays flat over long transfers — if it’s maintained on your hardware. The risk is a stale binary with a bug that someone else hit and nobody’s fixed, at a scale (days of uptime) where bugs surface.
High-speed performance rules of thumb
For getting genuinely fast, stable transfers, the downloader matters less than three things that apply to both:
- Right connection count. Set it to what your provider allows (often 100). Too few and you plateau below line speed; too many and you fragment. Both tools handle this via Settings → Servers → Connections.
- Fast, non-fragmented disk. Usenet saturates drives. Put
incomplete/andcomplete/on SSD or a RAID, never on the same slow spinning disk as the OS. - SSL on port 563. Encrypted links slightly raise CPU but keep UK ISPs from shaping you (see the UK throttling section). Both tools do SSL fine; enable it on server and client connections.
The Decision, Simplified
| Factor | SABnzbd | NZBGet |
|---|---|---|
| Speed (typical) | Great | Excellent on multi-core |
| Large-transfer stability | ✅ Huge soak-tested base | ⚠️ Flat RAM, but stale bugs |
| Resource use | Heavier | Much lighter |
| RAM on low-spec boxes | Poor fit | The reason to choose it |
| Active development | ✅ Active | ⚠️ Stalled |
| Community / guides | ✅ Huge | Smaller |
| Automation integration | ✅ Excellent | ✅ Excellent |
| Ease of setup | ✅ Best | Fine |
Use SABnzbd unless you’re running on a constrained device (low-RAM NAS, old Pi) and that device is struggling. That’s the honest dividing line. If you’re on a normal computer, a decent NAS, or a Docker host, SABnzbd is the better long-term bet — active development and the biggest community outrank a marginal speed win.
If your whole point is squeezing maximum throughput from a 2 GB Pi, NZBGet is arguably still the right call in 2026.
Setup Notes for Both
- SSL: whichever you pick, configure SSL/TLS on port 563 for both the download (server) and, where supported, the control (client) connections. See the privacy section of the setup guide.
- Connections: set the connection count to the max your provider allows; both tools handle this fine.
- PAR2: both auto-handle .par2 repair files from your indexer’s NZBs. More repair threads = faster repair but more CPU. Start at 1–2, raise only if a big repair feels slow.
- Stability: for multi-hundred-GB weeks, point both tools at SSD for the download dir, cap the connection count to your provider’s allowance, and let a completed transfer queue cleanly rather than stacking ten downloads at once.
- Docker: both have solid official images; run them behind your media automation stack.
Which Provider Feeds It?
The downloader is only as good as the spool it talks to. If you’re still deciding where to point SABnzbd or NZBGet, the honest comparisons are here:
- Best Usenet Providers UK 2026 — the full roundup.
- Cheapest Usenet providers — blocks vs unlimited, costed honestly.
- Usenet retention explained — the number everyone overpays for, plus the PAR2 science.
And if you landed here cold: what even is Usenet?.