New Living Translation
This disciple is the one who testifies to these events and has recorded them here. And we know that his account of these things is accurate.

American Standard Version
This is the disciple that beareth witness of these things, and wrote these things: and we know that his witness is true.

Berean Study Bible
This is the disciple who testifies to these things and who has written them down. And we know that his testimony is true.

Douay-Rheims Bible
This is that disciple who giveth testimony of these things, and hath written these things; and we know that his testimony is true.

English Revised Version
This is the disciple which beareth witness of these things, and wrote these things: and we know that his witness is true.

King James Bible
This is the disciple which testifieth of these things, and wrote these things: and we know that his testimony is true.

World English Bible
This is the disciple who testifies about these things, and wrote these things. We know that his witness is true.

Young's Literal Translation
this is the disciple who is testifying concerning these things, and he wrote these things, and we have known that his testimony is true.

John 21:24 Additional Translations ...