# How to change image URLs in a markdown string

> Learn how to rewrite image URLs inside a markdown string with a regex, replacing spaces with hyphens and pointing them to a /images/slug/ folder for Next.js.

Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2022-05-24 | Topics: [JavaScript](https://flaviocopes.com/tags/js/) | Canonical: https://flaviocopes.com/how-to-change-image-url-markdown/

I was trying to see if moving my blog (based on Hugo) to [Next.js](https://flaviocopes.com/nextjs/) was a good move (it wasn't) and I found a problem.

Hugo allows me to use spaces in images, which is handy especially as I use screenshots and I get those named as `Screen Shot 2022-...` by default. 

The Next.js markdown does not allow that. So I had a script that converted all images names to use hyphens instead of spaces

```
"Screen Shot 2022-..." 

=> 

"Screen-Shot-2022-..."
```

and then I replaced the post markdown content with that. 

Also I had to change the URL because Hugo allows a post to be in the same folder as the markdown file, while Next.js does not.

So I used a `/public/images/<SLUG>/` folder format to make each post image public.

Here's how I did that:

```js
import matter from 'gray-matter'

...

let { data: frontmatter, content } = matter(fileName)

const regex = /\!\[(.*?)\]\((.*?)\)/gm
let matches

while ((matches = regex.exec(content)) !== null) {
  content = content.replace(
      '](' + matches[2],
      `](/images/${slug}/${matches[2].replace(/ /g, '-').replace(/\//g, '')}`
  )
}
```