How to draw checkbox or tick mark in GitHub Markdown table?

Try adding a - before the [] or [x]. That's an - followed by a blank space .

Below is an example from Github blog.

### Solar System Exploration, 1950s – 1960s

- [ ] Mercury
- [x] Venus
- [x] Earth (Orbit/Moon)
- [x] Mars
- [ ] Jupiter
- [ ] Saturn
- [ ] Uranus
- [ ] Neptune
- [ ] Comet Haley

It appears like below:

Here's how one could do the same in a table:

| Task           | Time required | Assigned to   | Current Status | Finished | 
|----------------|---------------|---------------|----------------|-----------|
| Calendar Cache | > 5 hours  |  | in progress | - [x] ok?
| Object Cache   | > 5 hours  |  | in progress | [x] item1<br/>[ ] item2
| Object Cache   | > 5 hours  |  | in progress | <ul><li>- [x] item1</li><li>- [ ] item2</li></ul>
| Object Cache   | > 5 hours  |  | in progress | <ul><li>[x] item1</li><li>[ ] item2</li></ul>


- [x] works
- [x] works too

Here's how it looks:

Now emojis are supported! :white_check_mark: / :heavy_check_mark: gives a good impression and is widely supported:

Function | MySQL / MariaDB | PostgreSQL | SQLite
:------------ | :-------------| :-------------| :-------------
substr | :heavy_check_mark: |  :white_check_mark: | :heavy_check_mark:

renders to (here on older chromium 65.0.3x) :

I used ☐ (☐) for [ ] and ☑ (☑) for [x] and it works for marked.js which says it is compatible with Github markdown. I based my solution on answers for this question. See also this informative answer.

Update: I should have mentioned that when you do it this way, you do not need the <ul>, e.g:

| Unchecked | Checked |
| --------- | ------- |
| ☐   | ☑ |