The four questions that narrow it fastest

How big? Compare with something you know: a house cat, a labrador, a deer. Size alone rules out most of the candidates.
What shape? Long tail or short, bushy or bare; pointed muzzle or blunt; ears up or folded. Shape is what separates a fox from a coyote from a small dog at fifty meters.
How did it move? Bounding, trotting, waddling, gliding. Movement is often the only thing you saw clearly.
Where, and when? Range maps do a lot of the work. A species that does not live in your region is not what you saw, however much the photo looks like it.

When you have a photo

Crop to the animal, keep the background for context, and let the app read it. The profile gives the species, the taxonomy, habitat, diet and behavior, and a match score that tells you how cleanly the image read. A low score means take another photo, or lean on the four questions above.

When all you have is a track or a dropping

Photograph the sign with something for scale before you disturb it, then use the field-sign guides:

Moose tracks: A moose track is the largest hoof print on the continent: two crescent-shaped halves running about 4.5 to 5.5 inches long, pointed toward the direction of travel, with two dewclaws that often register behind them in snow or mud.
Bear scat: Black bear scat is a large tubular deposit, usually left in a coil or in segments 2 to 3 inches long and 1.25 to 1.5 inches across.
Deer tracks: A deer track is a split, upside-down heart: two pointed toes side by side, symmetrical, about 2.5 to 3 inches long in Maine's guidance and up to 4 inches in Missouri's.
Bear tracks: A black bear leaves two very different prints.
Coyote scat: Coyote scat is ropelike and twisted, averaging 3 to 4 inches long and about an inch across, usually packed with hair and bone.
Coyote tracks: A coyote track is a compact oval about 2.5 inches long and 2 inches wide, with four toes and toenail marks that nearly always print.
Mountain lion tracks: A mountain lion track is round, 2.75 to 3.75 inches wide, with four teardrop-shaped toes and no claw marks.
Raccoon tracks: Raccoon tracks look like small hands.
Wolf tracks: A wolf track is about 5 inches long by 4 inches wide, with four symmetrical toes, claws that clearly register, and a single lobe at the front of the foot pad.
Deer scat: Deer scat is a scattered pile of dark oval pellets, each about 0.5 to 1 inch long and 0.2 to 0.5 inch across, shiny when fresh and holding no recognizable pieces of food.

The pairs people mix up most

Coyote vs wolf: A gray wolf is roughly twice a coyote's size.
Coyote vs fox: A coyote outweighs a red fox two or three times over: 18 to 30 pounds against 7.5 to 15 pounds.
Frog vs toad: Skin and legs settle it.
Bobcat vs mountain lion: The tail decides it.
Hawk vs eagle: Scale is the first answer.

Questions people ask

How can I identify an animal from a picture?

Start with the four questions that narrow it fastest: how big was it, what shape was its body and tail, how did it move, and where were you. Then let the photo do the rest: Animal Identifier reads the species from the image and returns the profile with a match score, and the field-sign guides here cover the cases where you only saw a track or a dropping.

What if the photo is blurry or far away?

The app still returns its best read but with a lower match score, which is the honest answer. Crop to the animal, note the size against something in the frame, and compare the profile's habitat and range with where you were. A second, closer photo beats a guess.

Is there a free way to identify an animal?

Animal Identifier is free to download with a set of identifications. Your state wildlife agency's website and university extension pages, which the guides here cite, are free reference for tracks and scat.