bs4.FeatureNotFound: Couldn't find a tree builder with the features you requested: html5lib

You asked BeautifulSoup for the html5lib parser (BeautifulSoup(html, 'html5lib')) without having html5lib installed. Run pip install html5lib and the same line works. If you cannot install it, switch to 'html.parser', which ships with Python.

The error

bs4.FeatureNotFound: Couldn't find a tree builder with the features you requested: html5lib

Fix it

1. Install html5lib

python -m pip install html5lib

Expected: Successfully installed html5lib-1.1.

1. Re-run your parse line unchanged

python -c "from bs4 import BeautifulSoup; print(BeautifulSoup('hi', 'html5lib').get_text())"

Expected: prints hi.

1. Alternative without new installs

soup = BeautifulSoup(html, 'html.parser')

Expected: parses with the stdlib parser. Behavior differs slightly on broken markup, which is the whole reason people pick html5lib.

When this applies

• the FeatureNotFound message names html5lib
• you passed 'html5lib' as the parser, or a library did on your behalf

When it does NOT apply

• FeatureNotFound naming lxml means install lxml instead
• No module named 'html5lib' from a direct import is the same missing package without bs4 in the middle

Compatibility

All bs4 4.x with html5lib 1.1. html5lib is the most lenient parser bs4 supports, which is why guides recommend it.

Why it happens

BeautifulSoup is a tree API over pluggable parsers. Naming 'html5lib' selects that parser, and if it is not installed bs4 raises FeatureNotFound instead of guessing. The message names the missing feature set, so the fix is mechanical.

Edge cases

• html5lib is slower than lxml. Pick it for leniency on broken markup, not for speed.
• If html5lib IS installed but the error persists, it is the two-interpreter problem. python -m pip install html5lib targets the right one.