Your puppy barks constantly between eight and sixteen weeks and you can't always tell if it's a problem or just normal puppy behaviour. Barking is one of the few tools your puppy has to tell you something, and the fix only works if you know what they're actually telling you. Most owners treat every bark as the same problem and reach for the same response, which is exactly why it doesn't work.
This piece is for puppies. If you've got an adult dog and want the general version, how to stop excessive dog barking covers territorial barking, boredom, and being left alone for dogs past the puppy stage.
The five reasons puppies bark
Every bark your puppy makes falls into one of five categories. Get the category right and the fix is usually straightforward.
Demand barking
Sharp, repetitive barks aimed at you, with eye contact held the whole time. Shows up at the food bowl, the lead, a toy nobody will throw. It exists because it worked before, even once.
Alert barking
Sharp, sustained barking aimed at the edge of your puppy's space, a window, a fence line, the front door. Weight forward, ears up. Your puppy has decided watching the boundary is their job.
Frustration barking
Repetitive and flat, no real rhythm to it. Usually in the crate, at a gate, at a door they can't get through. Your puppy isn't reacting to anything outside, they're reacting to being stuck.
Anxiety barking
Lower-pitched, often broken up with whines. Weight backward, tail low, sometimes backing away from whatever set it off while still barking. This is distress, not confidence.
Play barking
High, short, yippy bursts with a loose, bouncy body and a play bow. Normal and developmentally appropriate. Only worth addressing if the excitement spills into other situations once play stops.

How to tell which one you're dealing with
Before you respond, read four signals. Get this wrong and your response makes the behaviour worse.
Direction of the bark. Aimed at you, that's demand. Aimed at the environment or boundary, that's alert or anxiety. Aimed at nothing specific, that's frustration.
Body weight shift. Forward, that's alert, confident, managing the boundary. Backward, that's anxiety, overwhelmed. A forward puppy and a backward puppy need opposite responses.
Eye contact with you. Present and sustained, that's demand barking. Absent, that's alert, anxiety, or frustration.
What happened one second before. A trigger appeared, that's alert, anxiety, or play. Your puppy wanted something, that's demand. Nothing happened at all, that's frustration.
The mistake that turns a normal puppy into a chronic barker
The mistake is specific: accidentally reinforcing demand barking through intermittent, delayed, or frustrated responses. Your puppy barks, you hold out for a couple of minutes, then break and make eye contact or move toward the bowl. Your puppy has just learned that barking for long enough works. A behaviour that sometimes produces a result is harder to shift than one that never does, and it only takes one person in the house responding occasionally to keep the whole pattern alive.
Demand Barking: What It Is and How to Stop Reinforcing It walks through the full four-step loop, the extinction burst most owners give up during, and a week-by-week protocol.

What to do about each type
Demand barking
Any response counts, even a sigh or a firm word. The fix is complete non-response until your puppy has settled, then giving them what they wanted on your terms, never mid-bark. See the link above for the full breakdown.
Alert and territorial barking
Alert barking is your puppy taking on a job nobody gave them: deciding who's allowed near the house. It needs a physical, silent handover of that job back to you, not a shouted "quiet" and not a treat to distract. How To Stop Excessive Dog Barking (That Actually Works) has the full silent redirect, plus what to do about barking from boredom or being left alone.
Barking at strangers and visitors
If the trigger is specifically an unfamiliar person, on the footpath or at the door, that's its own category, distinct from a general alert bark at a sound or a shadow. Puppies who don't meet a wide range of people before the socialisation window closes at 6 months are more likely to carry that reaction into adulthood. Puppy Barking at Strangers: The Silent Way to Fix It covers the full approach, on the lead and at the door.
Frustration barking
Don't let the crate door, gate, or pen open while the bark is happening, ever. The release comes during a pause, even a two-second gap of quiet. If it's happening at the same time most days, that's usually solved by more exercise and a calmer wind-down before your puppy is expected to settle, rather than needing a redirect on the bark itself.
Anxiety barking
This calls for a different approach entirely. Don't suppress it and don't tell your puppy it's okay, both skip past the actual problem. Be calm and physically present, position yourself between your puppy and whatever set them off, and keep enough distance that they can see the trigger without going over threshold. If the anxiety only shows up once you've left the house, that's a distinct problem with its own fix, and Puppy Separation Anxiety: What It Looks Like and What to Do covers it in full.
Play barking
Play barking isn't something to fix. Teach a clear start and a clear stop to play, using the same cue each time, so your puppy learns play has defined edges.
When to stop trying things and call a trainer
Call a trainer when anxiety barking is generalised rather than tied to a specific trigger. When demand barking has run for four or more weeks with consistent handling and hasn't dropped off. When alert barking is causing noise complaints and hasn't shifted in two to three weeks. When any barking pattern showed up suddenly after a specific event rather than developing gradually.
The Complete Puppy Program covers all five bark types alongside the rest of the first-six-months curriculum, and a meet and greet is free if you want to talk through what you're seeing first.