Microwave-safe
The maker says the item may be used in a microwave oven. It is about the container, not the food: Mepal explains that when the symbol is crossed out, it is often because the material ‘should not be heated in this way’.
Market convention
This symbol is a market convention: no law or public standard defines the drawing, so each maker draws its own and the meaning is whatever that maker says it is. This page follows 4 makers’ and retailers’ own keys.
- What it looks like
- Three or four horizontal wavy lines, on their own or inside a square that stands for the microwave. Some makers draw a whole microwave oven with waves in the window, or add the word MICRO; some draw a dish with wavy lines above it.
- Other names
- microwave safe symbol; microwavable; wavy lines symbol; MICRO
What it does not promise
Microwave-safe does not cover every lid, every food or every heating time. Several makers attach conditions: Nordic Houseware Group has a separate open-lid version, Sistema says to heat with the vent open, and Pyrex says its covers must be unsealed and laid off-centre and its glass must not be used for microwave popcorn or browning wrappers. Heating instructions for the food itself still apply.
Where makers differ
Mepal draws three waves in a square; Nordic Houseware Group draws a microwave oven with waves and the word MICRO, and has a second version with ‘OPEN LID’ for boxes whose lid must be lifted or removed. Whirlpool lists the squiggly lines, a picture of a microwave, a dish with four lines above it, and three lines over the word ‘micro’. Sistema engraves its symbol only on its microwave range and says products without it ‘cannot be used in microwaves’.
Often confused with
The maker says the item must not go in a microwave oven. Mepal gives the usual reason: the material ‘should not be heated in this way’.
Sources
No law defines this symbol, so the meaning is taken from makers’ and retailers’ own pages. Those marked as showing the icon draw or describe it; the others add conditions. Each was fetched and read on the date shown:
- Mepal : What do the symbols and specifications on a product mean? — Shows the ‘microwave safe’ icon — three wavy lines in a square — and the same icon crossed out: ‘This symbol shows whether you can put your product in the microwave. If there is a cross through it, the product cannot be used in the microwave.’ Checked 2026-09-24.
- Nordic Houseware Group : Understanding Symbols — Shows two icons: ‘Microwave Safe’ (a microwave oven with waves and the word MICRO) and ‘Microwave Safe with open Lid’ — ‘the lid must be lifted and/or removed from the bottom of the box when being used in the microwave oven’. Checked 2026-09-24.
- Whirlpool : Dishwasher Safe & Other Tableware Symbols — Shows a microwave-safe icon: such dishes are ‘usually stamped with a symbol that features several squiggly lines’; other versions are ‘an image of a microwave, a dish with four microwave lines above it and/ or three wave lines above the word “micro.”’ Checked 2026-09-24.
- Million Pack (food-packaging manufacturer, Ningbo) : What the Microwave Safe Symbol Looks Like and Means? (10 November 2025) — Calls three horizontal wavy lines ‘the most widely used microwave safe symbol’, and shows a second version: a square or rectangle standing for the microwave, with wavy lines inside. Checked 2026-09-24.
- Sistema: FAQ's — Its microwavable products carry ‘a microwave symbol which is engraved at the bottom of the product or printed on the label or carton’, and ‘Our products without engraved microwave symbol cannot be used in microwaves.’ The page does not draw the symbol. Checked 2026-09-24.
- Pyrex (US): Frequently Asked Questions — Pyrex covers are microwave safe only when ‘unsealed from the dish and lay off-center to allow steam to escape’, and Pyrex glassware must not be used ‘to microwave popcorn or heat foods in browning wrappers’. No icon is shown. Checked 2026-09-24.
Written in our own words; quotations are the sources’ wording.