How to Tell If Mason Jars Are Sealed: 3 Lid Checks

A sealed canning jar has a lid that stays firmly in place without the screw band and does not flex when you press its center. Let the jars cool undisturbed for 12 to 24 hours before you test them; a popping sound alone is not proof of a seal.

Set processed jars upright on a towel or cooling rack, with space between them, and leave them undisturbed for 12 to 24 hours. A lid may make a popping sound as it cools, but our team recommends waiting until the jar is fully cool to assess the seal.

Remove the screw band and look at the flat lid: its center should be slightly concave, not raised. Press the center with a finger; if it moves down and springs back, the jar is not sealed.

With the band still off, gently try to lift the flat lid at its edge using your fingertips. A properly sealed lid stays attached, but do not pry hard or lift the jar by the lid, which could disturb the seal.

A jar that closes tightly for pantry storage is not necessarily suitable for home canning. Use jars and two-piece lids intended for canning when preserving food; decorative or vintage-style storage jars should be used for dry goods unless they are specifically rated for the canning method you plan to use. For more on selecting and using an embossed storage jar, see our vintage embossed glass storage jar guide.

If a lid fails either test, do not put that jar on the shelf as a shelf-stable preserve. Refrigerate its contents promptly and use them within the time recommended for that food, freeze them in a freezer-safe container, or reprocess within 24 hours using a new lid and an approved recipe.