What the second feed changes, and what it leaves alone
It changes distribution. Current entering at both ends meets near the middle, so the worst-served section sits halfway along rather than at the far tip, and the fade at the tail goes away.
It leaves three things alone. The driver's rated output does not grow because you connected to it twice. An undersized supply cable is still undersized, and two thin pairs are two bottlenecks. And a published maximum is a manufacturer statement, so whether dual-end feeding extends it for a given item is worth confirming.
Two parallel branches, not a loop, and never reversed
Constant voltage tape branches out from the supply in parallel. A dual-end feed means two separate pairs leaving the same driver, one landing on the head of the run and one on the tail. Nothing is chained in series, and it is not one cable that leaves the driver, travels to the far end and returns.
Polarity has to agree at both ends. Reverse the pair at the far end and you have connected the supply across itself through the copper in the tape, which is a fault rather than a dim run. Parallel and series wiring for strip runs covers the topology.
Total the load as watts per foot times installed footage across everything on that supply, then add current headroom; LED Club guidance is currently at least 20 percent, and the figure should be confirmed before you specify. Voltage has to agree end to end, so a 24V run needs a 24V driver and a 24V controller, and 12V hardware stays with 12V tape. For the take-off at each end, a prewired strip-to-wire connector avoids soldering where tape width and pad layout match what the product lists, and terminations sit in the connector and cable listings. The line voltage side of a hardwired supply belongs to a licensed electrician working to the manufacturer instructions, local electrical code and the NEC.
Where a far-end connection behaves differently
Addressable pixel tape is the exception. Data travels one direction from the controller, so a connection at the far end is a power feed only and never a second data entry point. That product's documentation sets where power may be added. The same caution covers any strip not listed by its manufacturer for dual-end feeding, because silence is not permission.
Three things settle whether to feed from one end or both ends
First, the published limit against your finished length. If the run exceeds what the product allows on one feed, the decision has already been made for you.
Second, access at the far end. Can a cable reach it, and can you reach it again in two years? A cove with a chase behind it is easy. An under-cabinet run whose tail sits past a sink is not.
Third, what the run is doing visually. A length seen head to tail in one sightline shows a soft end plainly; a run broken by cabinet stiles or door openings hides the same gradient.
Where the far end is unreachable and the length exceeds the published limit, the honest answer is a shorter run.
