> For the complete documentation index, see [llms.txt](https://developers.oxylabs.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developers.oxylabs.io/products/web-scraper-api/features/custom-parser/writing-instructions-manually.md).

# Writing instructions manually

See how to write parsing instructions manually to handle edge cases or customize parsing logic.

While Custom Parser helps you automate data parsing with AI-powered features, you can also write parsing instructions manually using CSS and XPath expressions. This gives you the option to **handle edge cases** or **customize parsing logic** for specific scenarios.

Custom Parser requires these mandatory parameters when creating a job:

* `parse` set to `true`
* `parsing_instructions` containing a JSON object with your extraction rules

Once you're happy with your custom parsing logic, you can save the instructions as a reusable [parser preset](/products/web-scraper-api/features/custom-parser/parser-presets.md).

Check out our comprehensive guides below, where you can find practical examples, best practices for XPath expressions, and a complete reference of all available parsing functions.

{% content-ref url="/pages/oxrwg37AyLWH1P5TPzwI" %}
[Parsing instruction examples](/products/web-scraper-api/features/custom-parser/writing-instructions-manually/parsing-instruction-examples.md)
{% endcontent-ref %}

{% content-ref url="/pages/z3HuH3Sn6WT2loO8bw5e" %}
[Tips for writing XPath expressions](/products/web-scraper-api/features/custom-parser/writing-instructions-manually/tips-for-writing-xpath-expressions.md)
{% endcontent-ref %}

{% content-ref url="/pages/751P6A1HZSfgMAhsniMo" %}
[List of parsing functions](/products/web-scraper-api/features/custom-parser/writing-instructions-manually/list-of-functions.md)
{% endcontent-ref %}

{% content-ref url="/pages/LWprqEz9Iwufi0fbGjXn" %}
[Parsing function examples](/products/web-scraper-api/features/custom-parser/writing-instructions-manually/list-of-functions/function-examples.md)
{% endcontent-ref %}


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