URL Encoding - Critical Knowledge¶

Most Common Mistake

URL encoding is the #1 source of errors when using the Danish Parliament API. Failure to properly encode URLs will result in HTTP 400 errors or unexpected results.

The Golden Rule¶

Always use %24 instead of $ in OData query parameters.

L Wrong	✅ Correct	Result
`?$top=5`	`?%24top=5`	Works
`?$filter=id eq 1`	`?%24filter=id%20eq%201`	Works
`?$expand=Aktør`	`?%24expand=Akt%C3%B8r`	Works

Why This Matters¶

OData uses the $ character for system query options like $top, $filter, etc. However, $ has special meaning in URLs and shells, so it must be URL encoded as %24.

Complete Encoding Reference¶

Basic Characters¶

Space         %20
$             %24
&             %26
=             %3D (usually handled automatically)
'             %27
(             %28
)             %29

Danish Characters¶

ø             %C3%B8
å             %C3%A5
æ             %C3%A6
Ø             %C3%98
Å             %C3%85
Æ             %C3%86

Real Examples¶

Basic Queries¶

WrongCorrect

# This will fail
curl "https://oda.ft.dk/api/Sag?$top=5"

# This works
curl "https://oda.ft.dk/api/Sag?%24top=5"

Text Filtering¶

WrongCorrect

# This will fail
curl "https://oda.ft.dk/api/Sag?$filter=substringof('minister', titel)"

# This works
curl "https://oda.ft.dk/api/Sag?%24filter=substringof('minister',titel)"

Complex Queries¶

WrongCorrect

# Multiple issues
curl "https://oda.ft.dk/api/Sag?$filter=year(opdateringsdato) eq 2025&$top=10&$orderby=titel"

# Properly encoded
curl "https://oda.ft.dk/api/Sag?%24filter=year(opdateringsdato)%20eq%202025&%24top=10&%24orderby=titel"

Danish Text Searches¶

WrongCorrect

# Danish characters not encoded
curl "https://oda.ft.dk/api/Aktør?$filter=substringof('ø', navn)"

# Danish characters properly encoded
curl "https://oda.ft.dk/api/Akt%C3%B8r?%24filter=substringof('%C3%B8',navn)"

Programming Language Examples¶

Python¶

import urllib.parse

# Proper URL encoding
query = "$filter=substringof('klima', titel)&$top=5"
encoded_query = urllib.parse.quote(query, safe🔧&🔧)
url = f"https://oda.ft.dk/api/Sag?{encoded_query}"

# Or use requests which handles encoding
import requests
params = {
    '$filter': "substringof('klima', titel)",
    '$top': 5
}
response = requests.get('https://oda.ft.dk/api/Sag', params=params)

JavaScript¶

// Proper URL encoding
const params = new URLSearchParams({
    '$filter': "substringof('klima', titel)",
    '$top': 5
});
const url = `https://oda.ft.dk/api/Sag?${params}`;

// Or use encodeURIComponent for manual encoding
const filter = encodeURIComponent("substringof('klima', titel)");
const url2 = `https://oda.ft.dk/api/Sag?%24filter=${filter}&%24top=5`;

curl in Shell Scripts¶

#!/bin/bash
# Proper escaping in shell scripts
FILTER="year(opdateringsdato) eq 2025"
curl "https://oda.ft.dk/api/Sag?%24filter=${FILTER// /%20}&%24top=10"

Common Encoding Mistakes¶

1. Missing Dollar Sign Encoding¶

# L Will cause HTTP 400
curl "https://oda.ft.dk/api/Sag?$top=5"

# ✅ Correct
curl "https://oda.ft.dk/api/Sag?%24top=5"

2. Missing Space Encoding¶

# L Malformed query
curl "https://oda.ft.dk/api/Sag?%24filter=id eq 1"

# ✅ Spaces encoded
curl "https://oda.ft.dk/api/Sag?%24filter=id%20eq%201"

3. Danish Characters¶

# L May cause issues
curl "https://oda.ft.dk/api/Aktør?%24filter=substringof('ø',navn)"

# ✅ Properly encoded
curl "https://oda.ft.dk/api/Akt%C3%B8r?%24filter=substringof('%C3%B8',navn)"

4. Complex Boolean Logic¶

# L Parentheses not encoded
curl "https://oda.ft.dk/api/Sag?%24filter=(typeid eq 3) and (year(opdateringsdato) gt 2020)"

# ✅ Complete encoding
curl "https://oda.ft.dk/api/Sag?%24filter=%28typeid%20eq%203%29%20and%20%28year%28opdateringsdato%29%20gt%202020%29"

Testing Your Encoding¶

Use these test queries to verify your encoding works:

Test 1: Basic Query¶

curl "https://oda.ft.dk/api/Sag?%24top=1" | jq '.value | length'
# Expected: 1

Test 2: Text Filter¶

curl "https://oda.ft.dk/api/Sag?%24filter=substringof('forslag',titel)&%24top=1" | jq '.value | length'
# Expected: 1 (if results exist)

Test 3: Date Filter¶

curl "https://oda.ft.dk/api/Sag?%24filter=year%28opdateringsdato%29%20eq%202025&%24top=1" | jq '.value | length'
# Expected: 1 (if results exist)

Error Symptoms¶

If your URLs aren't properly encoded, you'll see:

HTTP 400 Bad Request¶

{
  "error": {
    "code": "400",
    "message": "Bad Request"
  }
}

Empty HTML Response¶

<!DOCTYPE html>
<html>
<head><title>400 Bad Request</title></head>
<body>
<h1>400 Bad Request</h1>
</body>
</html>

Shell Errors¶

bash: $top: command not found

Quick Reference Table¶

Character/Sequence	Encoding	Example Usage
`$top=5`	`%24top=5`	Pagination
`$filter=`	`%24filter=`	Filtering
`id eq 1`	`id%20eq%201`	Filter condition
`substringof('text', field)`	`substringof('text',field)`	Text search
`year(date) eq 2025`	`year%28date%29%20eq%202025`	Date functions
`(condition1) and (condition2)`	`%28condition1%29%20and%20%28condition2%29`	Boolean logic

Tools for URL Encoding¶

Online Tools¶

Command Line Tools¶

# Python one-liner
python3 -c "import urllib.parse; print(urllib.parse.quote(input()))"

# Node.js one-liner
node -e "console.log(encodeURIComponent(process.argv[1]))" "your text here"

Remember: When in doubt, encode everything! It's better to over-encode than under-encode with this API.