Eclipse glasses: what actually matters
For the partial phases, ordinary sunglasses are not enough. Use purpose-built solar viewers that comply with the applicable ISO 12312-2 standard and inspect them before use.
Ordinary sunglasses are not eclipse glasses
NASA states that regular sunglasses, no matter how dark, are not safe for direct solar viewing. Safe solar viewers are thousands of times darker.
Look for the applicable standard
NASA recommends viewers that comply with ISO 12312-2. Follow the manufacturer's instructions and discard damaged viewers.
Cameras and telescopes are different
Do not look through an unfiltered camera, binoculars or telescope while wearing eclipse glasses. Concentrated sunlight can cause serious injury. Optical devices need suitable solar filters secured over the front of the optics.
During complete totality
Only when the Sun's bright face is completely covered may observers inside the path of totality view directly without solar viewers. Put protection back on as soon as any bright sunlight reappears.
Safety source: NASA Eclipse Viewing Safety. This guide is educational and does not replace product instructions or professional advice.