A clogged nozzle is a blockage in the nozzle or the hot end that chokes the filament path. Flow drops or stops, the print goes thin or gaps, and you often hear the extruder click. Per Prusa’s clogged-nozzle guide, most blockages come from burnt residue, a nozzle that ran too cold, or filament that softened too high in the heat break.
A cold pull clears most clogs without tools. Clear it, then fix the cause so the next print does not jam again.
Your material changes the odds. PETG and flexible TPU clog more than PLA, and a wet spool can swell and jam.
The causes, ranked
| Likely cause | Fix | Severity |
|---|---|---|
| Burnt residue or clog | Run a cold pull to drag the blockage out, then push fresh filament through. | hi |
| Nozzle too cold | Raise the nozzle 5 to 10 C so the filament melts fully. | hi |
| Heat creep from a weak fan or long retraction | Fix the hot-end fan and cut retraction back. | md |
| Wet filament swelling | Dry the spool, then reprint. Wet filament can swell and jam. | md |
| Debris or a worn nozzle | Clean the nozzle out, or swap in a new one. | lo |
First fixes to try
Clear the path first, then remove what caused it. Reprint the same test after each step.
Run a cold pull
Heat the hot end, let it cool partway, then pull the filament out fast to drag the clog with it.
Raise the nozzle temp
Set the nozzle 5 to 10 C higher and push filament through to confirm clear flow.
Check the hot-end fan
Make sure the fan spins whenever the hot end is warm, so filament does not soften high in the heat break.
Dry the filament
If the jam came with popping or bubbles, dry the spool and reprint.
When quick fixes are not enough
When a cold pull does not hold, the hardware is the next place to look.
Remove and clean the nozzle
Unscrew the nozzle while warm, poke or soak it clear, or fit a new one.
Cut retraction back
If heat creep keeps clogging the path, reduce retraction so filament does not sit in the heat zone.
Reseat the PTFE tube
On a Bowden hot end, push the tube flush to the nozzle so there is no gap for filament to catch.
Material differences
PLA clogs the least, because it melts clean at a low temperature. PETG and flexible TPU clog more, since they run hotter and ooze, and TPU can fold inside the path. Any wet filament can swell and jam, so dry the spool first when clogs repeat.
Mistakes that undo the fix
A few common choices clear the jam but leave the cause in place.
Avoiddo not
- Only pushing fresh filament through, without fixing the fan or the retraction.
- Running the nozzle far above the range to push a clog through, which burns the filament.
- Forcing a needle through a cold nozzle, which can scratch and widen it.
- Skipping the dry step for PETG or TPU.
Key takeaways
- A clog chokes flow and shows up as under-extrusion or a clicking extruder.
- A cold pull clears most clogs without taking the hot end apart.
- Fix the cause, the fan and the retraction, after you clear the jam.
- Dry PETG and TPU first. Wet filament swells and jams.
For the full breakdown, the clogged nozzle guide goes deeper on the cold pull, and the filament storage guide covers keeping spools dry.
Related guides
Related
More in this area
Cross-reference
Sources & methodology
3 citations · reviewed 2026-07-10- 01Prusa Knowledge Base: Clogged nozzle and hot endaccessed 2026-07-09Tier 1
- 02Bambu Lab Wiki: Common print quality problems (clogs, extrusion)accessed 2026-07-09Tier 1
- 03All3DP: Clogged nozzle, cold or atomic pull methodaccessed 2026-07-09Tier 2