No！
If your running shorts have a built-in liner, you do not wear underwear with them. The liner is the underwear — that is the entire reason it is sewn in. Adding a second layer underneath cancels the two jobs the liner was engineered to do: move sweat off the skin, and keep fabric from rubbing against it.
We build these garments, so this is answered from the pattern table rather than from opinion. Below: what a liner is, the four constructions it comes in, why the answer is no, when the exceptions genuinely apply, and how a liner is put together. Honfit is a sportswear manufacturer in Guangzhou, and running shorts start at 20 pieces per style.
What Is a Liner? The Anatomy of a Lined Running Short
A liner is a second layer sewn inside the short, between the shell and the body. It is not a free gift of underwear tucked into the waistband. It is part of the garment's structure, fixed at the waistband and usually at the side seams, which is why cutting it out leaves a short that fits differently.
Liners come in four constructions, and the difference between them is a design decision rather than a quality ranking:
- Brief liner — a triangular inner brief. The most common construction, and the lightest.
- Boxer or trunk liner — a fitted inner short reaching partway down the thigh. Covers more, but makes no compression claim.
- Compression liner — a thigh-length inner short built with controlled negative ease, the 2-in-1 style. The most supportive and the hottest to wear.
- Linerless — no inner layer at all. The wearer supplies their own base layer.
The fabric is a lightweight performance knit in every case. Across the brands whose specs are published, the recipe converges tightly: 78 to 95% polyester with 5 to 22% elastane, at 95 to 140 grams per square metre. Zoot's running liners sit at 85/15 and 115 g/m²; Brooks uses 90/10; GOREWEAR 83/17 in an interlock knit; Kattun's lightweight mesh is 95/5 at 95 g/m²; and at the heavier end, 78/22 lands around 140 GSM. Anything in that band will behave like a liner should. Below it, the knit turns translucent under stretch. Above it, you have built a second pair of shorts.
Fabric weight splits by construction type more than by price. Mesh and brief liners perform best between 80 and 120 GSM. Compression liners need more opacity and more recovery, so they run 160 to 220 GSM. For context, the outer shell is usually heavier than the brief liner it contains: race split shorts run 90 to 120 GSM, daily training shorts 120 to 150, and 2-in-1 or trail shorts 150 to 180, typically with 5 to 12% elastane.
Why liners exist at all comes down to three functions. They hold everything in place so nothing shifts mid-stride. They wick, moving moisture into the shell where it can evaporate. And they relocate friction — instead of skin moving against a shell seam, a knit surface moves against skin, which is a far more forgiving interface. The last of those three is the one that matters most over distance, and it is the reason the liner exists rather than a recommendation to simply buy looser shorts.
So Do You Wear Underwear With Lined Shorts?
No, and the reasoning is worth spelling out because "just don't" is not an explanation.
The layer is already there. A liner provides the support and coverage that underwear provides. Wearing both is wearing two pairs of underwear — the equivalent of a belt and braces, or swimming in a swimsuit with underwear underneath. There is no functional gap for the second layer to fill.
The second layer adds friction rather than removing it. Two layers of fabric between skin and shell can shift against each other as you run. Every shift is a small shear force at the groin, and over thousands of strides those accumulate into chafing. A liner worn alone has one interface to manage. A liner plus underwear has three, and the middle one is doing nothing useful.
And it traps heat and moisture exactly where you least want either. The groin and gluteal region has a dense concentration of sweat glands. Adding a layer restricts airflow and holds moisture against skin, producing a warm, dark, damp environment — the conditions in which bacteria and fungi thrive. That is the mechanism behind jock itch and rashes, and for women it raises the risk of yeast infections. A moisture-wicking liner handles sweat far better than the cotton underwear most people would reach for, which absorbs water into the fibre, gains weight, and stays wet.
This is not a house opinion. Every published gear guide that addresses the question reaches the same conclusion, and the reasoning above is theirs as much as ours.
When the exception applies. There are legitimate reasons to wear something underneath. A liner that does not fit properly — too loose, riding up, or sized wrong — is a real problem, and the fix is either a different size or a different construction. Some wearers want more support than a brief liner provides, and some want more coverage for reasons including menstruation or stress incontinence. In those cases, choose a technical sports brief that is not cotton, cut with flat or bonded seams, and fitted snugly rather than compressively. The point is that the underlayer should be doing a job the liner is not, and it should be built for the same conditions. A cotton brief under a liner is the worst of both.
And there is a dissent worth reporting. One long-time gear editor argues the opposite: that unlined shorts plus a high-quality boxer brief is the better system, on the grounds that a good boxer brief is what every running short's liner is trying to be. It is a fair argument, and it holds up for shorter efforts — independent testing found that for short tempo runs, moisture-wicking underwear under ordinary shorts performed about the same as a lined 2-in-1, and in some cases felt better supported. The same testing found the 2-in-1 pulled ahead as distance increased, which is where the extra heat and moisture of a layered system becomes a real cost. So the honest position is not that one system wins everywhere. It is that a liner and underwear are alternatives, not layers.
Brief vs. Boxer vs. Compression vs. Linerless
Once you accept that the liner replaces underwear, the next question is which construction suits the running you actually do.
| Construction | Structure | Support and coverage | Heat | Suited to |
|---|---|---|---|---|
| Brief | Triangular inner brief, leg opening above the thigh | Basic support, medium coverage | Lowest | Lightweight shorts, hot conditions, faster efforts |
| Boxer | Fitted inner short, thigh length, no compression target | Coverage without compression | Moderate | Runners who want thigh coverage without pressure |
| Compression | Thigh-length inner short with controlled negative ease | Strongest hold and coverage | Highest | Daily training, 2-in-1 shorts, structured feel |
| Linerless | No inner layer | None — wearer supplies base layer | N/A | Runners with a preferred base layer already |
Length is not compression. This is the single most common specification error in the category, and it costs brands real money. A liner does not become a compression liner by being made longer. Compression comes from negative ease — the inner short is cut smaller than the body it fits — and it depends on the support target, the grading across sizes, and the fabric's recovery. A thigh-length liner with no negative ease is a boxer liner, and labelling it compression is a spec mismatch. If you are buying shorts and the product page says "compression liner" without describing fit or recovery, that is a claim to test rather than trust.
Choosing by distance. Brief liners suit shorter, faster running and warm weather, where minimal coverage is the point. Compression and boxer constructions suit longer efforts and cooler conditions, where support and coverage earn their extra heat. The line between them moves with the runner, not with a rule.
Can compression shorts be worn as underwear? Yes — that is precisely what they are for. A compression liner or a pair of compression shorts can be worn alone, or under looser shorts, and either is a complete system. The only thing to avoid is wearing them with underwear, for the same three reasons as above.
Women's and men's liners are separate patterns. Women's constructions typically run longer in the liner and cover more, which is a difference in the pattern block rather than a size adjustment. A brand building both lines needs both patterns drafted, not one scaled.
How We Build a Liner: Fabric, Seams and Gusset
Most coverage of this subject is written from the runner's side of the waistband. Here is the other side of it, because the construction details are what actually decide whether a liner chafes.
The seam is the whole game. A liner's failure mode is almost never the fabric. It is a raised seam edge pressing into skin for two hours. Flatlock sewing joins panels with a stitch that lies flat against the cloth, distributing pressure across the seam width instead of concentrating it on a ridge. An overlock finish does the opposite, leaving a proud edge on the inside. Every serious running brand specifies flatlock on liners, and it is worth being clear that this is a baseline rather than a premium feature — it is the minimum standard, and a liner finished with overlocked seams is a shortcut, not a budget option. There is a crude test anyone can run in a shop: turn the shorts inside out, run a thumb along the inner leg seam. If you can feel a ridge catch, put them back.
The gusset reduces the seam count. The crotch is where a liner is most likely to fail, so it gets its own panel. A gusset lets the pattern replace several converging seams with one shaped piece, and each seam removed is a friction point that no longer exists. The best gussets also do structural work: a stretch mesh gusset adds airflow and lets the liner move through a full stride without binding, and a triangular cut achieves the same with fewer pattern pieces.
Fabric choice is a weight-and-opacity trade. As covered above, brief liners live at 80 to 120 GSM and compression liners at 160 to 220. The knit needs to be hydrophobic enough to move moisture rather than hold it, elastic enough to recover after a full stride cycle, and opaque enough at the stretch it will actually see. That last constraint is the one brands underestimate. A fabric that looks solid on a flat swatch can turn translucent the moment it is stretched over a hip.
Waistband and leg opening carry load. On a lined short, the waistband often serves both shell and liner, so its elastic has to hold two layers without rolling. Leg openings on compression liners are where ride-up starts: without enough grip or the right hem geometry, the liner migrates upward through a run. Silicone grip tape solves it at the cost of a firmer feel against skin, and the trade is a decision to make deliberately rather than by default.
All of it is built to order. Our custom running shorts are made from a pattern developed for the liner construction you choose, at a minimum of 20 pieces per style.
Custom Lined Running Shorts: Options, MOQ and Team Orders
All four constructions are available. Brief, boxer, compression, and linerless are all produced in-house, which matters more than it sounds. Many factories tool up for one or two liner types and subcontract the rest, and a brand that wants to offer a lined and an unlined version at two price points — or a brief for summer and a compression for winter — usually has to split the order across suppliers. Producing all four under one roof means one pattern block, one fit standard, and one colour match across the range.
Minimum order. Running shorts start at 20 pieces per style. We do not take single-piece or individual orders: a one-off garment cannot absorb the cost of artwork, pattern grading, and a print run, and anyone quoting you a price for one is quoting a price they will not honour. A run club, a race team, or an event order clears that threshold immediately.
What can be specified. Inseam length — 3, 5, and 7 inch are the standard options. Liner construction, from the four above. Waistband type, including drawcord or elastic-only. Pocket configuration, including a liner-integrated phone pocket, which is one of the most requested features on a long-distance short and one of the easiest to get wrong if the pocket is added to the shell instead of the liner. Decoration by sublimation, screen print, or transfer. And the full size curve, men's, women's, and youth drafted separately.
Decoration on a liner-bearing short. Sublimation remains the default for full-colour work because the dye bonds into the fibre rather than sitting on top of it, so graphics add no weight and do not stiffen the garment. It requires polyester in the blend — 60 to 65% is the practical floor for a saturated print, and the base fabric must start white — which is not a constraint on running shorts, where the fabric is synthetic already. For a small placement logo, a soft-base screen print or a light transfer is fine. What does not work is a heavy plastisol print or a solid transfer film laid over a stretch liner, because both crack or block moisture exactly where the garment is meant to breathe.
Team and event orders. Most liner production is not retail. It is run clubs, race organizers, and charity teams ordering a unified set: consistent colour across the size range, names or numbers applied per garment, and a club logo sized and placed to read from a distance. Because every one of those variables is applied per piece, the run has to clear the minimum — 20 pieces per style — and a club of 20 is already there.
What to send with an enquiry. A first quote comes back usable when the message includes: quantity per style, the size breakdown, liner construction and inseam length, any reference garment or fabric preference, logo or artwork in vector format where possible, and colour references. The size breakdown and the liner choice are the two that get left out most often, and both change the price. The wider line is set out on our custom running shirts page, the shorts specifications on custom running shorts, and the sleeveless half of the same wardrobe — the race vest, its fabrics and its cuts — is covered in what a running singlet actually is.
Frequently Asked Questions
Do you wear underwear with lined running shorts?
No. The liner is designed to replace underwear, providing the support and coverage that underwear would. Wearing both adds a second layer that shifts against the skin, creating friction, and traps heat and moisture in an area with a high concentration of sweat glands.
Why do running shorts have liners?
Three reasons: to hold everything in place so nothing shifts mid-stride, to wick moisture away from skin into the shell, and to move friction off bare skin onto a knit surface, which is far more forgiving over distance.
Can you wear compression shorts as underwear?
Yes — that is what they are designed for. A compression liner or compression shorts can be worn alone or under looser shorts. What you should not do is wear them with underwear underneath, for the same reasons you would not layer underwear under any other liner.
Do you need underwear with unlined shorts?
With unlined shorts you supply your own base layer, so yes — unless you switch to a pair with a compression liner instead. If you do wear underwear, choose a technical synthetic brief with flat or bonded seams, never cotton, which absorbs sweat and holds it against the skin.
What is the minimum order for custom lined running shorts?
20 pieces per style. Brief, boxer, compression, and linerless liners are all produced in-house, so a brand can offer lined and unlined versions from a single supplier and a single fit standard.
