Can You Decompile a Python 3.14 `.pyc`? (Tested)

API_KEY = "sk-demo-314"

def check(user, key):
    if key == "PRO-2026":
        return f"welcome {user}"
    return "denied"

print(check("mithun", "PRO-2026"))

It has a hard-coded key and a license check — the two things people hope a .pyc hides. I compiled it with py_compile on Python 3.14; the file starts with the magic bytes 2b 0e 0d 0a (magic number 3627), which is what identifies it as 3.14 bytecode.

The go-to tool for modern bytecode is pycdc (Decompyle++) — it's what our .pyc Decompiler runs in the browser. Pointed at the 3.14 file, it refuses to load it:

Bad MAGIC!
Could not load file sample314.pyc

The pip-based decompilers are even further behind: uncompyle6 tops out around Python 3.8 and decompyle3 around 3.9 — neither runs on 3.14 bytecode at all. This isn't a bug; it's the normal lag. Every decompiler has to be taught each new version's magic number and opcodes by hand, so support for a brand-new release lands months later.

A .pyc is just a 16-byte header followed by a marshal-serialized code object — the exact structure the interpreter runs. Python's own marshal and dis modules read it natively on *any* version, including one no decompiler supports yet. Running them (on Python 3.14) against the same file recovered everything that matters:

import marshal, dis

with open("sample314.pyc", "rb") as f:
    f.read(16)                 # skip the 16-byte .pyc header (3.7+)
    code = marshal.load(f)     # the module's code object

dis.dis(code)                  # full bytecode listing
print([c for c in code.co_consts if isinstance(c, str)])

string constants recovered:
  ['sk-demo-314', 'mithun', 'PRO-2026', 'welcome ', 'denied']

# dis excerpt (module level):
LOAD_CONST    0 ('sk-demo-314')
STORE_NAME    0 (API_KEY)
LOAD_CONST    1 (<code object check ...>)
MAKE_FUNCTION
STORE_NAME    1 (check)

No decompiler, no matching interpreter version needed — the API key, the PRO-2026 license string, and the full control flow are all right there. You don't get clean .py back (you get bytecode plus constants), but for reading secrets or understanding logic it's usually enough, and it never hits a version wall. The interactive version of this is our Bytecode Disassembler, which now supports 3.14.

There's no fixed date — decompiler support for a new CPython release typically arrives weeks to months after it ships, as maintainers map the new opcodes. pycdc (which powers our browser tool) has the broadest coverage and reaches new versions first, so it's the one to watch; uncompyle6/decompyle3 are effectively frozen at 3.8/3.9. Until full 3.14 support lands, marshal + dis is the reliable bridge. For .pyc files from 3.12 and earlier, our .pyc Decompiler already returns readable source today — see the full method comparison.

"No decompiler supports my Python version yet" feels like protection, but the test shows it isn't: the strings and logic read straight out of the file with two standard-library calls. As with every other Python version, shipping .pyc is a cache format, not a lock. To actually protect 3.14 code:

1. Obfuscate the source before compiling — rename identifiers and encrypt string literals with our free Python Obfuscator so even the recovered bytecode/constants are meaningless.
2. Keep real secrets off the client — a hard-coded key survives in co_consts verbatim; load it from the environment or a backend (protecting API keys in Python).
3. For the strongest bar, compile to a native module (Cython .pyd/.so or a Nuitka binary) so there's no code object to marshal.load at all.

More on why bytecode isn't protection in can .pyc files be decompiled and is Python obfuscation secure?.