Annealed glass (ordinary float glass)

Annealed glass is ordinary, untreated float glass — the standard glass you get before any strengthening. It has NOT been heat-treated, so when it breaks it shatters into large, sharp, dangerous shards — which is exactly why it is not classed as safety glass. That's the key difference from toughened (tempered) glass, which is heat-treated to be much stronger and to crumble into small, blunt pebbles when it fails. Annealed glass is fine where safety glass isn't required (e.g. small picture frames, some interior panes), but it must not be used for doors, large or full-height panes, low-level glazing, shower screens or anything people can walk into — those legally/safely need toughened or laminated glass. It's also why a cracked patio or shower door pane can't just be swapped for cheap ordinary glass — it has to go back in as safety glass. If you're unsure what's in an existing pane, a glass repair and replacement specialist can identify it and replace it with the correct safety grade.