What is symmetrical internet, and do you need it?

Symmetrical internet means your upload speed equals your download speed, such as 300/300 Mbps. Most fiber plans work this way. Cable, DSL, 5G and satellite plans are asymmetrical: upload is usually a small fraction of download, often a tenth or less. You need symmetrical service if you regularly send large files, back up to the cloud, stream live or have several people on video calls at once. For streaming and browsing, an asymmetrical plan is fine.

What symmetrical and asymmetrical look like

Plan names show the difference once you know where to look:

• Symmetrical: Verizon's Fios fiber tiers are sold as 300/300, 500/500 and so on, according to its network performance page. Its 1 Gig plan lists up to 940 Mbps down and 880 Mbps up on wired connections.
• Asymmetrical: On the same page, Verizon's 5G Home plan "up to 300 Mbps" lists typical speeds of 85–300 Mbps down and 10–20 Mbps up. Starlink's specifications list 25–220 Mbps down and 5–20 Mbps up.

Even the US broadband benchmark is asymmetrical. The FCC's 100/20 Mbps standard asks for one-fifth as much upload as download.

Why upload is usually slower

Most people download far more than they upload. CableLabs, the cable industry's research body, says a typical customer's upstream use is only about 10% of their downstream use. Networks were built to match.

Cable splits a shared line unevenly. A cable connection carries upload and download over the same coaxial line, divided into frequency ranges. Operators give most of that range to download. CableLabs lists the maximum capacity of DOCSIS 3.1, today's common cable standard, as 10 Gbps down and 1–2 Gbps up, shared among many homes on the same node.

DSL works the same way. The "A" in ADSL stands for asymmetric. The line is split so that most of its capacity goes to download.

Wireless upload is harder. On 5G and satellite, your gateway or dish usually transmits with much less power than the tower or satellite it talks to, which limits how much it can send back.

Fiber has room to spare. Fiber carries so much capacity that providers can offer the same speed both ways without squeezing download.

Who needs symmetrical internet

Use your upload speed, not your download, to decide. You'll benefit from a symmetrical plan if you:

• Back up large amounts to the cloud. A 50 GB photo backup takes about 11 hours at 10 Mbps up and about 1 hour 7 minutes at 100 Mbps up (50 × 8,000 ÷ speed).
• Send large video files for work. Editors, photographers and anyone sharing raw footage wait on upload every day.
• Stream live. Twitch recommends 6,000 kbps for 1080p at 60 fps, a steady 6 Mbps that has to fit alongside everything else in the home.
• Run several security cameras that upload to the cloud. Ring lists up to 15 Mbps of upload per 4K camera.
• Have several people on video calls at the same time. Each HD call needs a few Mbps up. Zoom recommends 3.8 Mbps up for 1080p.
• Host anything at home, such as a game server, a media server for family outside the home, or remote access to work files.

Who doesn't

If your household mostly streams, browses, games and makes the occasional call, an asymmetrical plan with 20 Mbps or more of upload is usually enough. As a rule of thumb, 10–20 Mbps covers one or two people on calls with headroom. What is a good upload speed breaks it down by activity, and is 50 Mbps upload good covers the point where most homes stop noticing a difference.

Symmetrical vs a big asymmetrical plan

Take a symmetrical 300/300 fiber plan and a hypothetical 1,000/35 cable plan. They are hard to compare on download alone. For a home that uploads a lot, the fiber plan will often feel faster, even though its download is lower:

• Uploading a 10 GB video takes about 4.4 minutes at 300 Mbps and about 38 minutes at 35 Mbps (10 × 8,000 ÷ speed).
• Downloading the same file takes about 4.4 minutes at 300 Mbps and about 80 seconds at 1,000 Mbps.

A slow upload also hurts everyone else. When one device fills the upload, calls and games in the rest of the home can lag, even though the download is idle. Why is my upload speed slow covers that and other causes.

Is cable catching up?

Cable networks are adding upload capacity. CableLabs' DOCSIS 4.0 standard supports up to 10 Gbps down and 6 Gbps up, which it says allows multi-gigabit symmetrical services. Rollout depends on your provider and area, so ask what upload is actually sold at your address. Fiber vs cable internet compares the two today.

Check your own upload

Run the speed test on a computer connected by Ethernet and compare the upload with your plan. If you're shopping for a new plan, put the upload speed on your checklist next to price and download; how to choose an internet plan has the rest of the list.