When using Icons8 assets for free, add one visible link to icons8.com anywhere your audience can see it. One link in one place is enough — you don't need to attribute every individual icon.
Where to put it depends on your project:
Website: footer or imprint page
Mobile app: About section and app store description
Desktop software: About dialog
Chrome extension: Web Store description and Settings page
WordPress plugin: Settings page and plugin listing
Document or presentation: anywhere in the document
Game: Credits section
YouTube video: description or credits
E-commerce listing: footer or item description (eBay, Amazon, etc.)
GitHub project: README or project description
Social media: mention @icons8 in a post or profile
Academic paper or journal: References section — a text mention like "Icons by Icons8 (icons8.com)" works when a clickable link isn't possible
Physical product or print: include the link on the product's website, packaging, or item description
The link can point to icons8.com or to the specific icon you used. Just make sure it's visible to your audience.
If you'd rather skip attribution entirely, any paid plan removes the requirement.