Etag can refer to:

• HTTP ETag, entity tag, part of the HTTP protocol for the World Wide Web

• etags, the utility that comes with Emacs

• NERC Tag, also known as E-Tag, a transaction on the North American bulk electricity market

• e-TAG, an electronic tolling system used on tollways in Australia

• European Technology Assessment Group, a network of scientific institutions

• European Technical Approval Guidelines, drafted by the European Organisation for Technical Approvals