A sewing machine makes a lockstitch with one needle thread and a bobbin thread, and it is the machine you build a garment with: seams, darts, zips, hems, buttonholes and topstitching. A serger, called an overlocker outside North America, uses 3 or 4 threads carried by needles and loopers to sew a seam, trim its edge and wrap it in thread in a single pass, which makes it the fastest way to finish seams and the best way to sew stretchy seams on knits. You need a sewing machine; a serger is a second machine that saves time and gives a factory finish, and many people sew well for years without one.
| Feature | Sewing machine | Serger (overlocker) |
|---|---|---|
| Stitch | Lockstitch: needle thread and bobbin thread | Overlock: 2–4 threads from needles and loopers, no bobbin |
| Threads | 1 needle + 1 bobbin | 3 or 4 on most home models (2 to 8 on some) |
| Trims the edge | No | Yes, with a knife ahead of the needles |
| Seam stretch | Only with zigzag or stretch stitches | Stretches with the fabric by design |
| Can it sew a dart, a zip, a buttonhole, topstitching? | Yes | No |
| Can it sew into the middle of a piece? | Yes | No, it works along an edge |
| Threading | One thread and a bobbin | 3–4 threads in a set order, color-coded; air threading on some |
| Speed | 600–1,100 stitches per minute | 1,100–1,500 stitches per minute |
| Price tier | Entry-level upward | Entry-level sergers cost about as much as an entry-level sewing machine |
What does a serger actually do?
A serger has a knife that trims the fabric edge to a set width, then one or two needles stitch a seam while two loopers wrap thread over and under the cut edge. The result is a seam that is sewn and finished in one pass, with the thread wrapped around the raw edge so it cannot fray. The stitch is the one you see inside almost every ready-to-wear garment.
The common stitches on a home serger:
- 4-thread overlock: two needles and two loopers. The second needle row makes the seam strong enough to be the only seam on T-shirts, leggings and sweatshirts.
- 3-thread overlock: one needle and two loopers. Used to finish the edges of woven seams that are sewn on the sewing machine, and for light knits.
- Rolled hem: a narrow 3-thread stitch that rolls the fabric edge under; the hem on napkins, scarves and chiffon ruffles.
- Flatlock: a loose 3- or 2-thread stitch that pulls flat for sportswear seams.
Sergers have differential feed, two sets of feed dogs that can run at different speeds. Set faster in front, it stops knits from stretching into a wavy seam; set slower, it stops thin wovens from puckering. It is the control that makes serging knits so reliable.
What can a sewing machine do that a serger cannot?
Almost everything that is not an edge. A serger sews along the cut edge of the fabric, with the knife trimming as it goes, so it cannot:
- sew a dart, which starts at the edge and ends in the middle of the piece,
- insert a zip, sew a buttonhole or attach a button,
- topstitch or edgestitch,
- sew a seam and then press it open: an overlocked seam is pressed to one side,
- sew a precise 1.5 cm (5/8 in) seam allowance by the pattern lines; the serger trims the allowance off.
That last point matters with patterns. Sewly and most pattern companies include 1.5 cm (5/8 in) seam allowances on wovens and 1 cm (3/8 in) on knits. On a serger the standard stitch is about 6 mm (1/4 in) wide, so on a 1 cm allowance you trim away 4 mm and on a 1.5 cm allowance you trim away 9 mm. You align the fabric with a guide for the stitching line, not the raw edge.
What does a serger do better?
Seam finishing. Zigzagging every seam allowance of a lined dress on a sewing machine takes an hour; serging them takes ten minutes, and the result looks cleaner. If you sew a lot of wovens that fray, such as linen and viscose, this alone can justify the machine. The guide to finishing seams without a serger shows what the alternatives cost in time.
Knit seams. A 4-thread overlock stretches with the fabric and recovers, and the differential feed keeps the seam flat. A sewing machine does this with a narrow zigzag or a lightning stitch, and it works, but it is slower and the seams are bulkier. The guide to sewing knit fabrics on a regular machine shows how far a sewing machine goes.
Speed. With no bobbin to run out and a top speed near 1,300 stitches per minute, a serger sews a T-shirt in twenty minutes once the pieces are cut.
Rolled hems. Nothing on a sewing machine matches a serged rolled hem on sheer or fine fabrics.
Can you sew clothes with only a serger?
For knit garments with no closures, yes. A T-shirt, leggings, a sweatshirt and a knit dress can be made entirely on a serger, with the hems done by a twin needle on a sewing machine or by a coverstitch machine, or turned up by hand. Some people own a serger and a coverstitch and no sewing machine, but that is a sportswear setup.
For woven garments, no. Darts, zips, buttonholes, facings and topstitching all need a sewing machine. If you are buying your first machine, buy the sewing machine.
Is threading a serger really that hard?
It was. Older sergers needed the threads in a precise order with tweezers through the loopers, and a broken thread meant starting over. Modern sergers have color-coded thread paths printed on the machine and a lower looper threader, and some models (Baby Lock, and the Juki and Bernina air-threading models, at the time of writing in October 2026) thread the loopers with a puff of air. Even on a basic serger, threading takes a few minutes once you have done it three times, and the tie-on method, where you knot new threads to the old ones and pull them through, makes changing colors quick.
Most sewists thread their serger once with a neutral grey or beige thread and leave it, since the stitching is inside the garment.
Which sergers are widely used at home?
At the time of writing (October 2026), the Brother 1034D and its successors are the entry-level reference, with 3- and 4-thread overlock and differential feed. The Juki MO-654DE and MO-1000 (air threading), the Janome 8002D and the Bernette b44 are the next step in sturdiness and quieter running; Baby Lock sergers are known for air threading and automatic tension at a higher price. All of them sew 3- and 4-thread overlock and a rolled hem; the differences are threading, noise and how they handle thick seams.
Which should you choose?
- You own nothing yet: a sewing machine. It makes every garment, and it finishes seams with a zigzag or an overcast stitch until you decide whether a serger is worth it.
- You sew mostly wovens and finish seams with French seams or bias binding: you may never need a serger.
- You sew wovens that fray and you dislike zigzagging: a serger will save you hours per garment.
- You sew knits regularly, or you want to sew T-shirts, leggings and activewear for your family: a serger, as soon as you can. A 4-thread overlock is the right seam for a sweatshirt or a T-shirt, and the twin needle on your sewing machine handles the hems.
- You want professional-looking hems on knits as well: a serger first, a coverstitch later; the coverstitch vs serger comparison explains what each does.
- You have space for one machine only: a sewing machine with an overcast foot and an overcasting stitch gets closer to a serged finish than a plain zigzag.