Converting a hardwired fixture to plug-in

For a hanging fixture - a pendant or a chandelier - buy a swag conversion kit with a 14-foot cord. The Aspen Creative 21042A is the purpose-built one; the Gypsy Color kit does the same for about half as much and adds an inline switch. For a wall sconce, you do not need a swag kit at all - an 8-foot cord set is the whole job.

This is the most useful trick in renter lighting, because it removes the constraint that limits everything else. Once a fixture does not need a ceiling box, you can put light anywhere there is an outlet and something to hang from - and you are no longer choosing from the small range of fixtures sold as plug-in.

Outline rather than instructions - your kit will come with its own and those take precedence. Everything here is done with nothing plugged in.

1. Find the fixture's supply leads. Every hardwired fixture has two or three short wires emerging from its canopy, which is what an electrician would have joined to the ceiling wiring.
2. Join the cord to those leads with proper wire connectors - the ribbed or marked conductor to the fixture's neutral, the smooth one to its live. A ground wire, if there is one, is connected to the fixture's ground.
3. Secure the cord so it carries no weight. The chain or the hook takes the fixture; the cord is only ever carrying current. This is the single most important point on this page.
4. Fit the ceiling hook into something structural - a joist, or a proper cavity anchor rated well above the fixture's weight. A hook in bare drywall is how fixtures end up on the floor.
5. Run the cord to the wall along the ceiling, down to the outlet, and tidy it up - the options are in how to hide a plug-in fixture cord.

Aspen Creative 21042A - the purpose-built kit. A chandelier conversion kit with 14 feet of cord, made for this job rather than assembled from lamp parts.
Who it is for: anyone hanging a real chandelier or a heavy pendant, where you want hardware intended for the weight. Who should skip it: anyone converting a wall sconce, which needs nothing like this much cord, and anyone on a budget - the Gypsy kit does the same job.
Cons: the most expensive kit here; white cord shows against anything but a white ceiling; the hook and anchor are still your responsibility; and you lose the wall switch.

The Original Gypsy Color conversion kit - the value pick. Same 14-foot reach at roughly half the price, and it includes an inline switch - which matters more than it sounds, because a converted fixture has no wall switch any more.
Who it is for: most people converting a pendant in a rental. Who should skip it: anyone hanging something genuinely heavy, where the sturdier kit is worth the difference.
Cons: no load rating published for the cord; white only; an inline switch dangling on a cord is functional rather than elegant.

Asjeumt 8 ft. cord set with switch, 2-pack - for wall sconces. A sconce already has its own bracket and carries its own weight, so there is no swag and no hook - it just needs a cord. Two per pack, which is what a pair of sconces either side of a bed needs.
Who it is for: anyone converting hardwired wall sconces, which is the commonest version of this job. Who should skip it: anyone converting a ceiling fixture - 8 feet will not reach - and anyone who does not want to make the connections themselves.
Cons: you join it to the fixture leads yourself; no gauge or amperage published; a white cord down a wall is visible unless you channel it.

DiCUNO socket-to-outlet adapter - the no-conversion shortcut. If the room already has a working ceiling socket, this turns it into an outlet and the fixture plugs straight into the ceiling with no cord run at all.
Who it is for: anyone with a bare ceiling socket who wants to hang something from near that same point. Who should skip it: anyone whose fixture needs a ground, since these are two-prong, and anyone whose ceiling socket is nowhere near where the light should be.
Cons: no ground; the fixture hangs from the ceiling fitting rather than a proper hook, so this only suits light fixtures; you lose the original bulb socket.

The real cost of converting a fixture is not money, it is the wall switch. A converted fixture is controlled at the plug, which in practice means it gets left on or gets turned off by crawling behind furniture.

There are two good fixes and both are renter-safe. Put the plug on a remote control outlet or a smart plug, then stick a wireless wall remote where a switch would be. The result behaves like a wall switch and comes off the wall when you leave.

If dimming matters too, decide that at the same time - plug-in dimmers and screw-in socket adapters are the two routes that need no wiring.