Why is using a table in Next.js throwing a hydration error?

Question

In this code, I have a problem on using tag. when I use tr tag the error occurs.It says that Unhandled Runtime Error Error: Hydration failed because the initial UI does not match what was rendered on the server.

import React from 'react'
import {useState} from 'react'


const port = () => {
  return (
    <div className="ml-14">
      <div className="profile">
        <h1 className="mt-5 font-bold">Nasvirat</h1>
        <p className="mt-5">total balance : </p>
      </div>
      <div className="portfolio">
        <h2 className="mt-7">Holding</h2>

        <table>
        <tr>
          <th>Firstname</th>
          <th>Lastname</th>
        </tr>
        <tr>
          <td>Peter</td>
          <td>Griffin</td>
        </tr>
        <tr>
          <td>Lois</td>
          <td>Griffin</td>
        </tr>
        </table>
      </div>
    </div>
  )
}

export default port

do u have idea why this happen and how to fix it.

Answer 1

This is an open issue in the Next.js repo. The issue is coming from the fact that you do not have <tbody> or <thead> wrapping your rows.

Although they are not specified to mandatory for correctly rendering the table, next.js somehow cannot identify this.

My assumption is there is a difference in the code that is run on the server and on the client because of this.

Try adding this:

        <table>
        <tbody>
        <tr>
          <th>Firstname</th>
          <th>Lastname</th>
        </tr>
        <tr>
          <td>Peter</td>
          <td>Griffin</td>
        </tr>
        <tr>
          <td>Lois</td>
          <td>Griffin</td>
        </tr>
        </tbody>
        </table>

It is noteworthy, that browsers add a tbody inside the table automatically . So even if you skip it, it will end up in your DOM code. This is for older HTML versions as mentioned in the answer. Here is a demo for that. Check the code and compare it with the actual DOM that is rendered.

I am guessing next.js does not add the tbody by default when generating on server side. This is what causes the mismatch.