Stop Looking at Flat Code: Get Custom Astro Syntax Highlighting for Notepad++ (With XML Code)

If you are a fan of minimalist, local-first development frameworks like Astro, you already know how fast, lightweight, and efficient it is for building content-driven websites.

But if you also happen to love the lightning-fast launch speed of Notepad++ for quick edits, file comparisons, or lightweight coding, you’ve likely run into a frustrating roadblock:

❌ No native syntax highlighting for .astro files.

Opening an Astro component only to see a wall of monochrome text is a massive productivity killer. Because Astro blends HTML, CSS, frontmatter JavaScript, and JSX-like expressions all into a single file, standard HTML highlighting just doesn’t cut it.

The good news? You don’t have to manually configure every single keyword. I have pre-built a User Defined Language (UDL) XML configuration for you.

Here is how to install it in less than 60 seconds. 👇

🛠️ The 3-Step Quick Installation

Copy the XML code block below and save it on your computer as astro-npp.xml.
Open Notepad++ and navigate to Language > User Defined Language > Define your language…
Click Import…, select your astro-npp.xml file, and restart Notepad++.

Boom! Your .astro files will now automatically render with crisp, structured syntax coloring.

💾 The Astro UDL Configuration Code

<?xml version="1.0" encoding="UTF-8"?>
<NotepadPlus>
    <UserLang name="Astro" ext="astro" udlVersion="2.1">
        <Settings>
            <Global caseIgnored="no" allowFoldOfComments="yes" foldCompact="yes" forcePureLC="1" decimalSeparator="." />
            <Prefix Keywords1="no" Keywords2="no" Keywords3="no" Keywords4="no" Keywords5="no" Keywords6="no" Keywords7="no" Keywords8="yes" />
        </Settings>
        <KeywordLists>
            <Keywords name="Comments"> </Keywords>
            <Keywords name="Numbers"> </Keywords>
            <Keywords name="Operators1">= + - * / % ^ &amp; | ! &lt; &gt; ? : . , ;</Keywords>
            <Keywords name="Operators2">( ) [ ] { }</Keywords>
            <Keywords name="Folders">{ }</Keywords>
            <Keywords name="Keywords1">html head body div span a p br hr img input button form label ul ol li table tr td th thead tbody section article aside header footer nav main figure figcaption h1 h2 h3 h4 h5 h6 pre blockquote code em strong i b u small mark ins del sup sub canvas script style meta link title Fragment</Keywords>
            <Keywords name="Keywords2">id class style src href alt title type name value placeholder checked selected disabled readonly required pattern min max step autofocus autocomplete for method action enctype target rel media async defer charset lang dir hidden role viewport response time date datetime-local number range email tel url color file image submit reset button text search password onload onclick onchange oninput onsubmit onmouseover onmouseout client:load client:idle client:visible client:media client:only define:vars define:slots set:html is:inline is:global lang transition:name transition:persist transition:animate transition:animation</Keywords>
            <Keywords name="Keywords3">let const var function if else for while do switch case break continue return default import export from as new class extends super this static constructor typeof instanceof in of void delete throw try catch finally yield await async arguments true false null undefined NaN Infinity</Keywords>
            <Keywords name="Keywords4">type interface enum namespace implements extends keyof infer readonly any unknown never void</Keywords>
            <Keywords name="Keywords5">color background border margin padding font size weight family text align transform display position top right bottom left width height min-width max-width flex grid float clear list style transition animation opacity z-index box-shadow overflow visibility</Keywords>
            <Keywords name="Keywords6">true false null undefined NaN Infinity</Keywords>
            <Keywords name="Keywords7"> </Keywords>
            <Keywords name="Keywords8"> </Keywords>
        </KeywordLists>
        <Styles>
            <WordsStyle name="DEFAULT" styleID="11" fgColor="000000" bgColor="FFFFFF" fontName="" fontStyle="0" fontSize="" />
            <WordsStyle name="COMMENTS" styleID="1" fgColor="808080" bgColor="FFFFFF" fontName="" fontStyle="2" fontSize="" />
            <WordsStyle name="LINE COMMENTS" styleID="2" fgColor="008000" bgColor="FFFFFF" fontName="" fontStyle="2" fontSize="" />
            <WordsStyle name="NUMBERS" styleID="4" fgColor="FF00FF" bgColor="FFFFFF" fontName="" fontStyle="0" fontSize="" />
            <WordsStyle name="KEYWORDS1" styleID="5" fgColor="800000" bgColor="FFFFFF" fontName="" fontStyle="1" fontSize="" />
            <WordsStyle name="KEYWORDS2" styleID="6" fgColor="0000FF" bgColor="FFFFFF" fontName="" fontStyle="1" fontSize="" />
            <WordsStyle name="KEYWORDS3" styleID="7" fgColor="0000A0" bgColor="FFFFFF" fontName="" fontStyle="1" fontSize="" />
            <WordsStyle name="KEYWORDS4" styleID="8" fgColor="008080" bgColor="FFFFFF" fontName="" fontStyle="1" fontSize="" />
            <WordsStyle name="KEYWORDS5" styleID="9" fgColor="800080" bgColor="FFFFFF" fontName="" fontStyle="1" fontSize="" />
            <WordsStyle name="KEYWORDS6" styleID="10" fgColor="000080" bgColor="FFFFFF" fontName="" fontStyle="1" fontSize="" />
            <WordsStyle name="OPERATORS" styleID="12" fgColor="000000" bgColor="FFFFFF" fontName="" fontStyle="1" fontSize="" />
            <WordsStyle name="DELIMITERS1" styleID="14" fgColor="A31515" bgColor="FFFFFF" fontName="" fontStyle="0" fontSize="" />
            <WordsStyle name="DELIMITERS2" styleID="15" fgColor="A31515" bgColor="FFFFFF" fontName="" fontStyle="0" fontSize="" />
            <WordsStyle name="DELIMITERS3" styleID="16" fgColor="A31515" bgColor="FFFFFF" fontName="" fontStyle="0" fontSize="" />
            <WordsStyle name="DELIMITERS4" styleID="17" fgColor="0056B3" bgColor="FFFFFF" fontName="" fontStyle="1" fontSize="" />
        </Styles>
        <Delimiters>
            <Delimiter name="STRING1" open="&quot;" close="&quot;" escape="\" />
            <Delimiter name="STRING2" open="'" close="'" escape="\" />
            <Delimiter name="STRING3" open="`" close="`" escape="\" />
            <Delimiter name="COMMENTLINE" open="//" close="" consecutive="yes" />
            <Delimiter name="COMMENT1" open="/*" close="*/" />
            <Delimiter name="COMMENT2" open="&lt;!--" close="--&gt;" />
            <Delimiter name="COMMENT3" open="---" close="---" />
        </Delimiters>
    </UserLang>
</NotepadPlus>

🎨 Why This Matters for Your Workflow

Astro uses code fences (---) to separate the backend JavaScript component script from the HTML template.

This custom configuration ensures that:

Frontmatter blocks are visually isolated.
Astro hydration directives (client:load, client:visible) stand out immediately.
Component tags don’t get lost in regular HTML markup.

As developers, our tooling should adapt to our workflow, not the other way around. Customizing your environment—even the lightweight tools—minimizes cognitive load and keeps you in the flow state longer.

Are you building with Astro lately? Do you still use lightweight text editors like Notepad++ for quick hotfixes, or are you fully committed to heavy IDEs? Let’s discuss on Linkedin! 👇