What Does Black Mold Look Like? Photos and Look-Alikes

Black mold is usually described as dark green to black, and it can look slimy when wet. It spreads in irregular patches on damp, cellulose-rich materials like drywall, wood, and ceiling tiles.

If you are looking at a dark patch and trying to decide how worried to be, here is the part most pages skip: color and texture can suggest that you are looking at mold, and that it is worth taking seriously. They cannot tell you which mold it is, and you don't need to know: CDC says all molds should be treated the same with respect to potential health risks and removal. This guide shows what black mold actually looks like, surface by surface, how to tell it apart from the things people mistake for it, and what to do once you are fairly sure.

In This Guide

What black mold looks like: color, texture, and pattern
On different surfaces: drywall, wood, ceilings, showers
Is it black mold, or something else?: the look-alikes
You can't confirm it by sight: and why you rarely need to
What to do if it looks like black mold: the next step
Black mold appearance FAQ: quick answers

What black mold looks like

Black mold has four signals you can read at a glance: its color, its texture, the way it spreads, and where it grows. None of them confirms the species, and even together they suggest mold rather than prove it, but they tell you what deserves a closer look.

What black mold actually looks like

Four signals that suggest mold. None of them tells you the species.

Color

Dark green to black. “Black” is misleading; many molds look dark.

Texture

Can look slimy and shiny when wet; other molds can too, so texture is a clue, not an ID.

Pattern

Irregular patches spreading from a moisture source, not straight lines or even dots.

Where

On damp cellulose: drywall, wood, ceiling tiles, or cardboard that has stayed wet.

Color

Black mold is usually dark green to greenish-black, not the true jet black the name suggests. In good light it can read as charcoal gray or very dark brown, and it often looks darker when it is wet. Color describes what you are seeing, but it will not confirm a species: a colony's color can change as it ages, and several different molds fall into the same dark range.

Texture

Black mold can look slimy, gelatinous, and faintly shiny when it is wet. Texture is a clue rather than an identification, though: other molds can look slimy when wet too, and texture can't confirm the species any more than color can. Whatever the texture, avoid dry brushing, scraping, or fanning a patch, which puts spores and fragments into the air. On drywall, ceiling tile, or wood that has stayed wet, leave it undisturbed until you know how far it goes.

Macro of dark green-black mold on one surface: a wet-looking, shiny edge on the left and a duller, matte area on the right. — Dark mold can look wet and shiny in one spot and dull in another. Texture is a clue, not an identification, and dry brushing or fanning any growth puts spores in the air.

Growth pattern

Black mold grows in irregular, organic patches that spread outward from a moisture source, not in straight lines or evenly spaced dots. It grows on cellulose (drywall paper, wood, ceiling tiles, or cardboard), and CDC says constant moisture is required for its growth. That is why black mold tends to show up around chronic leaks, condensation, and old water damage, though a single leak can do it if the material stays wet long enough. Small dark specks clustered near a damp corner can grow into a larger patch if the moisture stays.

Are tiny black dots mold? Often, and not automatically. A cluster of small black or dark green specks near a damp corner, a leak, or a window that sweats is a common way mold shows up, and it can spread outward and start to smell musty if the moisture stays. Dots that are perfectly uniform, hard to the touch, or sitting on a surface with no moisture history are more likely soot or dust. No household test settles it, though: how a spot behaves under a damp cloth is a clue rather than proof, and a stain left after cleaning doesn't by itself show that mold remains. If the spots come back, or the surface stays damp, the moisture and the extent need another look.

What black mold looks like on different surfaces

Black mold reads differently depending on what it is growing on, because the material affects whether growth stays on the surface or can reach into it, though the look alone can't tell you which. Here is what it tends to look like in the places it shows up most.

On drywall and walls

On painted drywall, black mold often appears as a raised, fuzzy patch that returns after you clean it. The paint film is non-porous, but the drywall behind it is porous and holds moisture, so growth that looks like a surface stain can extend into the board. A common pattern is dark growth climbing from behind a baseboard or spreading around a window, with the paint faintly bubbled above it. Bubbled or peeling paint over a dark patch means moisture is getting into the wall, not just sitting on it; where it is coming from still needs finding. The cause-and-fix breakdown, pattern by pattern, is in why mold grows on walls and how to fix it.

Dark green-black mold spreading upward from behind a white baseboard on a painted bedroom wall, in an irregular fan of fuzzy patches with the paint faintly bubbled above it. — On painted walls, dark growth often climbs from behind the baseboard. Bubbled paint above it means moisture is getting into the wall; finding where it comes from is the next step.

On wood and framing

On bare wood, black mold follows the grain in dark green-black streaks and can grow into the surface. You see it on floor joists, studs, and subfloor in basements and crawl spaces, and on the backs of trim and cabinets. Bare wood takes up moisture, so growth below the surface here usually needs more than a wipe-down; wood is judged case by case, the wood beneath can darken, and badly affected framing is often cut out and replaced. Wood that has gone soft has decay as well as mold, which is worth having looked at. If the growth is in a basement or crawl space, see black mold in the basement, and for roof-line framing, black mold in the attic.

Dark green-black mold growing along the grain of a bare wood floor joist in a basement, in irregular streaks with the wood darkened around it. — On wood framing, black mold follows the grain and can grow into the surface. Bare wood is judged case by case, and growth here often needs more than a wipe-down.

On ceilings

On ceilings, black mold usually shows up as a dark, spreading patch below a moisture source, such as a roof leak, a plumbing leak from the floor above, or condensation. It can look like a fuzzy stain that keeps growing, sometimes ringed by a brown water mark. Ceiling growth is worth treating as a signal that moisture is reaching that spot, from a leak above or from condensation, so the fix starts with finding which. For attic and roof-line growth, see black mold in the attic.

In showers, tile, and grout

In a shower, black growth along grout lines and caulk is often what people call mildew, and where it grows can't tell you the species. It feeds on soap film in the spots that stay wet between showers. Tile is non-porous and grout can hold growth below its surface, but shower growth tends to be a cleaning and ventilation problem. The exception is when growth spreads from the tile onto painted drywall or the ceiling, or keeps returning even with good ventilation and regular cleaning, or there are signs of a leak, damaged grout or caulk, or loose tile; that is a reason to check for moisture behind the surface. For the full surface-by-surface playbook, see black mold in the shower.

On carpet, behind wallpaper, and window frames

On soft and hidden surfaces, black mold often looks like dark staining rather than a raised patch, which makes it easy to miss. On carpet and padding it appears as dark blotches, usually from a spill or a slow leak underneath. Behind wallpaper it grows where paste and trapped moisture feed it, so a bubbling or discolored seam can hide a colony. On window frames and sills it follows the line where condensation pools. In all three, a musty smell can be the first thing you notice, and a persistent one with no visible source is worth investigating for hidden moisture or growth.

Is it black mold, or something else?

Plenty of dark marks are not mold at all, and plenty of dark mold isn't Stachybotrys. Before you assume the worst, check what you are seeing against the common look-alikes. The useful clues are whether it is raised or flat, how it behaves when you clean it, and whether it keeps coming back, and none of them is proof on its own.

What gets mistaken for black mold, most often: soot and dust from candles, vents, and heaters; a dried water stain; efflorescence, the white crystalline powder on concrete and brick; and paint that has bubbled or darkened over a damp wall, which is a sign of water in the wall rather than mold itself. Mildew isn't on that list because it isn't a look-alike so much as the common name for flatter mold growth. The other half of the confusion is real mold that isn't Stachybotrys: Cladosporium, Aspergillus niger, and Alternaria all grow black or dark green and can look the same on a wall. The first group tends to lie flat and wipe away or dissolve. The second can't be told apart by eye, and for deciding what to do it doesn't need to be.

What you see

Usually

The tell

What to check

Dark, fuzzy, raised patch

UsuallyMold

The tellRaised, spreads in irregular patches, often a musty smell

What to checkTreat as possible mold; the material and the moisture decide what you do

Black soot or dust film

UsuallyNot mold

The tellFlat, gritty, collects near vents and baseboards, wipes away

What to checkLook for a source nearby: a candle, heater, or vent

Brown or yellow ring

UsuallyNot mold

The tellFlat discoloration from a past leak, no raised growth

What to checkOld water stain; check for active damp behind it

White crystalline powder

UsuallyNot mold

The tellOn concrete or brick, sparkly, dissolves in water

What to checkEfflorescence, a mineral salt; mold does not dissolve

Flat gray or white film

UsuallyMaybe mold

The tellCan be soap scum or dust; if it is growth, it is the flatter kind often called mildew, which is still mold

What to checkClean or remove it by the material, not the name; mold vs mildew

None of these checks confirms mold on its own. If it is raised, spreading, or sits where water has been, treat it as possible mold; if it keeps coming back after cleaning, the moisture and the extent need another look.

The two that fool people most are soot and efflorescence. Soot and dust from candles, vents, or heaters collect in flat, gritty, feathered streaks that follow airflow and wipe away with a cloth, where most mold sits raised off the surface. Efflorescence is the white, crystalline powder that shows up on basement concrete and brick; the quick test is water, because efflorescence dissolves and mold does not. If you want the full color-by-color rundown of every household mold, see the full mold identification chart and photos.

Flat black soot and dust streaking a wall above a baseboard heater, following the airflow path in feathered vertical lines, sitting on the surface with no raised or fuzzy texture, a common black-mold look-alike. — Not all black marks are mold. Soot and dust from vents and heaters lie flat in feathered streaks and wipe away. Most mold sits raised off the surface and spreads in irregular patches; texture is a clue, not proof.

You can't confirm toxic black mold by sight

Color and texture can suggest that you are looking at mold. They cannot tell you the species, and they cannot confirm so-called toxic black mold. CDC's NIOSH says the color of mold does not necessarily indicate that it is more or less dangerous, and several ordinary molds look just like the one people fear. Cladosporium, Aspergillus niger, and Alternaria all appear black or dark green, and on a wall they can be indistinguishable from Stachybotrys chartarum.

Here is the part that saves people a lot of worry: you do not need the species name to act. The CDC advises treating all mold the same for health and cleanup, so confirming whether a patch is Stachybotrys does not change what you should do next, which is to find the moisture and remove the growth. Where a species genuinely has to be documented for a defined reason, such as an insurance claim, that takes laboratory identification rather than a closer look, and routine spore-trap or microscopy analysis generally identifies a genus or broad fungal group rather than a species anyway.

When the answer would change what you do, for a claim, a home sale, or growth you can't size up yourself, the next step is to get a professional mold assessment rather than guess from a photo. An assessment starts with the building's history, a visual inspection, and a look for the moisture; sampling is used where it answers a defined question. It can reduce the uncertainty, but no assessment can promise certainty.

What to do if it looks like black mold

If you are fairly sure you are looking at black mold, start by not making it worse. Avoid dry brushing, scraping, or running a fan across it, which puts spores and fragments into the air. If it is on drywall, ceiling tile, or wood that has stayed wet, leave it undisturbed until you know how far it goes. Take photos for your records, then size up the job.

The EPA's rule of thumb is the place to start: if the moldy area is smaller than about 10 square feet, which is roughly a 3 foot by 3 foot patch, in most cases a homeowner can handle it. For more than that, the EPA points to its guidance for larger remediation jobs, and after sewage or other contaminated water it says to call a professional who has handled that kind of damage. Material is a separate question: porous materials that go moldy may have to be thrown away, and a contaminated HVAC system shouldn't be run. Our own advice is narrower than the EPA's: black mold on a hard, non-porous surface, under that size, is the case where careful do-it-yourself cleanup is reasonable.

The full step-by-step, including the safe way to handle a small patch, is in the guide on how to get rid of black mold. For anything bigger, or anything you are not sure about, an assessment is cheaper than guessing wrong.

Black mold appearance FAQ

The questions that come up most often, with the short answer first.

Frequently Asked Questions

What does toxic black mold look like?

So-called toxic black mold (Stachybotrys chartarum) is usually described as dark green to black, and it can look slimy when it is wet. The honest answer, though, is that you cannot confirm the species by looking at it: other molds look the same, and CDC's NIOSH says the color of mold does not necessarily indicate that it is more or less dangerous. You don't need the species to act, either. CDC says all molds should be treated the same with respect to potential health risks and removal, so what decides the response is what the growth is on, how far it has spread, and where the water is coming from.

What does harmless black mold look like?

Looking can't answer that. Several common molds, Cladosporium, Aspergillus niger, and Alternaria among them, look black or dark green and can look identical to Stachybotrys on a wall, and appearance can't sort molds into harmless and hazardous ones. CDC's NIOSH says the color of mold does not necessarily indicate that it is more or less dangerous, and CDC says all molds should be treated the same with respect to potential health risks and removal. So the useful question isn't which mold it is but what it is growing on and where the water is coming from.

What color is black mold?

Despite the name, black mold is usually described as dark green to greenish-black rather than a true jet black, and it can read as charcoal gray or very dark brown depending on the light and how wet it is. Color describes what you are seeing; it doesn't identify it. Many molds look dark, and a colony's color can change as it ages, so color can't confirm a species. CDC says you don't need to know the type to deal with it.

What does early-stage black mold look like?

Small growth often shows up as dark green or black specks and spots, clustered near a damp corner, a leak, or a water stain, and it can spread outward in irregular patches if the moisture stays. A small patch is easier to deal with than a large one, but how it looks can't tell you how far it has gone into the material; that depends on the material and how long it has been wet. Clean or remove it according to what it is growing on, and fix the moisture feeding it.

Is all black-colored mold black mold?

No. Many household molds appear black or dark without being Stachybotrys chartarum, including Cladosporium, Aspergillus niger, and Alternaria. You cannot tell them apart by color, and per the CDC you do not need to: all molds should be treated the same with respect to potential health risks and removal. Where a species genuinely has to be documented for a defined reason, such as an insurance claim, that takes laboratory identification, not a closer look.

What does black mold look like on wood?

On bare wood, black mold tends to follow the grain in dark green-black streaks and patches and can grow into the surface, sometimes darkening the wood. Wood that has gone soft has decay as well as mold, and that is worth having looked at. Bare wood takes up moisture, so growth that has worked below the surface usually needs more than a wipe-down; wood is judged case by case, and badly affected framing or trim is often cut out and replaced during professional remediation.

Are tiny black dots mold?

Often, but not automatically. A cluster of small black or dark green specks near a damp corner, a leak, or a sweating window is a common way mold shows up, and it can spread and start to smell musty if the moisture stays. Perfectly uniform dots, hard marks, or specks on a dry surface with no moisture history are more likely soot or dust. No household test settles it: how a spot behaves under a damp cloth is a clue, not proof, and a stain left after cleaning doesn't by itself show that mold remains. If the spots come back after cleaning, or the surface stays damp, the moisture and the extent need another look.

What is commonly mistaken for black mold?

Soot and dust from candles, vents, and heaters; dried water stains; efflorescence, the white crystalline powder on concrete and brick; and paint that has bubbled or darkened over a damp wall. Soot and dust tend to lie flat and wipe away, efflorescence dissolves in water, and stains and bubbled paint point to water rather than to mold itself, though all of these are clues, not proof. Mildew isn't a look-alike so much as the common name for flatter mold growth. The other confusion is real mold that isn't Stachybotrys: Cladosporium, Aspergillus niger, and Alternaria all grow black or dark green and can look identical on a wall. Color can't separate them, and for deciding what to do you don't need to, because CDC says all molds should be treated the same.

What to do next

What black mold looks like suggests it is mold and that it is worth taking seriously. It does not tell you the species, and per the CDC it does not need to, because all molds should be treated the same with respect to potential health risks and removal. So find the water, avoid uncontrolled disturbance, and deal with the growth based on its size and the material it is on. Keeping that material dry and fixing the moisture source is what makes it less likely to come back.

This guide is for educational purposes only and is not a substitute for professional advice. Health information is summarized from CDC and EPA mold guidance; verify any specific health concern with a healthcare provider. Always consult certified professionals for mold situations in your home.