Is it mold or mildew?
Mildew is a surface fungus. It's usually flat, powdery, white or gray, and it lives on damp bathroom surfaces. Mold is fuzzy or slimy, often dark, and it roots into drywall, wood, and fabric. The difference matters because one is a spray-and-wipe job and the other can mean cutting out material.
Question 1 of 6
What color is it?
What does the texture look like?
What is it growing on?
What happens when you wipe it with a damp cloth?
Does the area smell?
Has that spot ever been wet from a leak or flood?
Roof leak, pipe leak, overflow, or flooding. Shower steam does not count.
Your result
This quiz reads visual clues. It can't identify a species and it isn't a lab test or medical advice. When in doubt, treat it as mold.
Mold vs mildew at a glance
| Clue | Mildew | Mold |
|---|---|---|
| Color | White, gray, yellowish | Black, green, brown, blue, or mixed |
| Texture | Flat, powdery | Fuzzy, raised, or slimy |
| Where | Shower tile, grout, window sills, damp fabric | Drywall, wood, ceilings, carpet, ducts, anywhere a leak has been |
| Wipe test | Comes off clean | Stains, or comes back |
| Smell | Little to none | Musty, earthy |
| Fix | Clean and ventilate | Stop the water, then remove or clean the material |
Mildew is technically a kind of mold, so the line is about behavior, not biology. What matters for you is whether the growth is on the surface or in the material.
Frequently asked questions
Is mildew dangerous?
Mildew in a shower is mostly a nuisance. It can bother people with allergies or asthma, and it means the room is staying too damp. Clean it, fix the ventilation, and it stays gone.
Can black mildew be mold?
Yes. Dark growth on caulk or grout is often Cladosporium or Aureobasidium, which are molds even though people call them mildew. On a hard surface they clean up the same way. On drywall or wood, they are a mold problem.
Does the bleach test really work?
It is a rough field test, not proof. Mildew and many surface stains lighten quickly with bleach. Mold in the material tends to stay dark because the color is below the surface. Use it alongside the wipe test, not alone.
When should I stop guessing and call someone?
When the patch is bigger than about 10 square feet, when there was a leak, when the smell is strong, or when someone in the house has asthma or a weak immune system. See Do I need a pro? for the full checklist.
- No-obligation phone consultation
- Vetted local mold pros
- You decide whether to book