Can You Put Mason Jars in the Freezer?

Short answer: yes, with three rules. Use a straight-sided jar with no shoulder, leave at least 1 inch of headspace (1½ inches for half gallon and larger), and chill the contents in the fridge before they go in the freezer. Break any one of those and you'll find glass in your freezer.

Rule 1: leave enough headspace

Water expands about 9% when it freezes. Soup, stock and sauce are mostly water, so they push outward with real force as they solidify. A full jar has nowhere to send that expansion except into the glass.

Jar size	Headspace to leave
Pint (16 oz)	1 inch
Quart (32 oz)	1 inch
Half gallon (64 oz)	1½ inches

Rule 2: straight sides only — no shoulders

This is the one most people miss. A jar that narrows at the top — the classic “shouldered” profile — traps the expanding ice below the neck. The contents freeze into a plug wider than the opening and push straight out against the shoulder, which is the weakest geometry on the jar.

A straight-sided jar lets the ice rise unobstructed. If you can slide a spatula straight down the inside wall without hitting a taper, it's freezer-safe.

Rule 3: cool it in the fridge first

Glass cracks from thermal shock — a fast temperature change across the thickness of the wall. Hot soup into a cold freezer is the textbook way to break a jar, and it may not crack immediately; it can fail hours later or when you next handle it.

1. Let the contents cool on the counter to roughly room temperature.
2. Refrigerate for at least 4 hours, ideally overnight.
3. Only then move to the freezer.

Reverse the same rules on the way out: thaw in the fridge, never in hot water or a microwave straight from frozen.

Wide mouth is easier than regular mouth

Not a safety issue, a practical one. A frozen block slides out of a wide mouth jar under warm running water. Out of a regular mouth jar it doesn't — you end up waiting for it to thaw enough to spoon out, or worse, chipping at it.

What not to freeze in glass

• Carbonated anything. Expansion plus pressure equals a burst jar.
• Jars filled to the brim — see rule 1.
• Chipped or cracked jars. A flaw that survives room temperature will not survive freezing.
• Jars with shoulders — see rule 2.

How long does food keep in a frozen jar?

The jar isn't the limiting factor — glass is impermeable, so it actually beats most plastic for preventing freezer burn. Stock and soup hold quality for around 4–6 months, sauces about 3–4, and anything dairy-based rather less. All stay safe indefinitely at 0°F; it's texture and flavour that decline.