Good alt text for a reaction GIF communicates what the image contributes in context. It does not need to narrate every frame, identify an unfamiliar actor, or explain the entire history of a meme.
Begin by deciding whether the GIF adds meaning or merely decorates a message that already says everything necessary.
Describe the relevant reaction
For a GIF responding to a completed task, “A person nods in approval” can be more useful than a detailed inventory of clothing and background objects. If a visible caption changes the meaning, include the caption or its meaning.
Do not invent an identity or source when you do not know it. “A character looks around in confusion” is clearer and more honest than a guessed show title.
Avoid starting every description with “GIF of.” The surrounding interface may already identify it as an image, and the important information is the reaction itself.
Avoid redundant announcements
If the message says “Thank you, that fixed it” and the GIF is only decorative applause, repeating the same meaning can make the experience noisier. In ordinary HTML, a decorative image can use an empty alternative text when the context genuinely makes it unnecessary.
A selectable GIF in a picker is different: the control needs an accessible name so the user can choose it. A decorative-image decision should not leave the selection button unlabeled.
The W3C image decision tree helps distinguish informative, functional, and decorative images.
Separate content from action
A picker button might be named “Choose quiet applause,” while its preview control says “Play preview.” These labels tell the user what activating the control will do. Do not make both actions share an ambiguous “GIF” label.
For sent messages, include essential acknowledgments in ordinary text. Alternative text should not be the only place where a deadline, error explanation, or next step appears.
Review generated descriptions
Provider titles and descriptions can be useful raw material, but they may be vague, humorous, or unrelated to your use. GIFs.so exposes those fields in its API; consuming applications should decide whether they suit the current context.
If an assistant writes a description without seeing the animation, do not present it as verified visual analysis. Review the media when possible and preserve uncertainty otherwise.
Use the accessibility guide alongside alt text. A well-described loop still needs appropriate motion controls and keyboard behavior.