Short answer
Alligators and crocodiles are different kinds of crocodilian reptile. For the two native US species, an American alligator generally has a broad, rounded snout; an American crocodile has a narrower, tapering snout. On an American crocodile, the enlarged fourth tooth of the lower jaw is visible when the mouth is closed. On an American alligator, the lower teeth are normally concealed. 1
This page focuses on American alligators and American crocodiles. A useful US comparison should name those species rather than turn their distinguishing features into universal rules for every crocodilian worldwide. 2
On this page
At a glance
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| Feature | American alligator | American crocodile |
|---|---|---|
| Scientific name | Alligator mississippiensis. | Crocodylus acutus. |
| Snout | Broad and rounded. | Narrower and more triangular. |
| Teeth with mouth closed | Lower teeth normally hidden. | Enlarged fourth lower tooth visible on each side. |
| Typical adult appearance | Dark gray to nearly black. | Usually lighter, grayish green or brownish gray. |
| Usual US habitat | Primarily freshwater wetlands. | Particularly coastal, brackish, and saltwater habitats in southern Florida. |
| US distribution | Much of the Southeast. | Concentrated in southern Florida. |
| Does habitat alone identify it? | No; it can enter brackish and occasionally salt water. | No; a location is supporting evidence. |
Sources: appearance 1 3; scientific names, range, and habitat 2 3.
What each thing is
The American alligator is a large aquatic reptile native to the southeastern United States. Its broad head and usually dark adult coloration are useful recognition features. The Florida Fish and Wildlife Conservation Commission describes a range extending from southeastern Oklahoma and eastern Texas to North Carolina and Florida. 3
The American crocodile is a crocodilian found in coastal southern Florida and in parts of the Caribbean, Mexico, Central America, and northern South America. The National Park Service identifies southern Florida as the place where the two native US species coexist. 2
Alligator and crocodile are the narrower names. Crocodilian is the useful shared label when discussing both without deciding which one an observation shows. 2
Key differences
Head shape and teeth provide anatomical clues. The broad-versus-tapered snout contrast is useful, but the tooth arrangement adds another feature to compare. A confident identification should fit several visible characteristics and the likely species in that area. 1
Their habitat patterns differ without being absolute. American alligators usually occupy freshwater environments. American crocodiles are associated particularly with coastal waters in southern Florida. Yet alligators can occur in brackish water and occasionally salt water, so “salt water equals crocodile” is too strong. 2 3
Color is supplementary. Alligators often look darker, but algae and floating vegetation can change their apparent color. The familiar image of a green alligator may partly reflect material on its back rather than its underlying coloration. 3
How to tell them apart
Compare an existing photograph, a distant observation, or a wildlife agency’s identification image. Look for the combination of snout shape, visible teeth if the mouth is already closed, and overall appearance. Consider location as another clue. 1
These are observation criteria, not a reason to move closer or provoke an animal into showing its teeth. A partly submerged head, poor angle, or distant silhouette may not contain enough information to distinguish the species. The Florida wildlife agency explicitly notes that inexperienced observers can find the distinction difficult. 1
Where they overlap
Both are crocodilians adapted to life around water. Both are ectothermic: they regulate temperature behaviorally, including basking and moving between warmer and cooler surroundings. Both are predators whose diets can include fish and other animals. 2 3
They can occupy the same broader region in southern Florida. Seeing a crocodilian there therefore does not resolve the species before its characteristics are considered. 2
Edge cases
Young animals look different from adults. The Florida comparison guide describes young American alligators as dark with yellowish striping, while young American crocodiles have a lighter background with dark markings. An adult-color shortcut may fail on a juvenile. 1
An open mouth is not a temperament label. The National Park Service explains that American crocodiles may bask with their mouths open as part of temperature regulation. The posture alone does not tell us that the animal is directing aggression toward an observer. 2
Global generalizations need a separate comparison. Stories about other crocodile species do not automatically describe American crocodiles. In particular, reputation is not a reliable species-identification feature. 2
Why the distinction exists
The names identify related reptiles with different anatomy, ranges, and ecological patterns. Keeping the species explicit makes those differences useful: it allows a statement about coastal southern Florida to be assessed against the actual animals present there. Without that scope, a memorable identification rule can become an unsupported global claim.
Common misconceptions and examples
- “Anything in salt water must be a crocodile.” American alligators can enter saline habitats. 3
- “A green reptile must be a crocodile.” Algae can make an alligator appear greener. 3
- “A broad snout proves the answer from any photograph.” Angle and incomplete visibility can conceal the relevant anatomy.
- “The two never share a region.” Southern Florida contains both native US species. 2
Sources
Sources checked October 3, 2026. The comparison is expressly limited to the native US species.
- Florida Fish and Wildlife Conservation Commission — Differences Between Crocodiles and Alligators. Species identification features.
- National Park Service — American Crocodile: Species Profile. Range, coexistence, anatomy, and behavior.
- Florida Fish and Wildlife Conservation Commission — American Alligator. Range, color variation, freshwater preference, and saline exceptions.