How to Convert Lines to a Comma-Separated List or Custom Delimiter

Developers frequently receive data as one value per line but need it as a single delimited string.

Input:

alpha
beta
gamma

Output:

alpha,beta,gamma

Duck Cloud's Text Separator replaces line breaks with a custom separator directly in the browser.

Common separators

Different systems expect different delimiters:

Comma:

alpha,beta,gamma

Pipe:

alpha|beta|gamma

Semicolon:

alpha;beta;gamma

Space:

alpha beta gamma

Choose the delimiter based on the destination format.

Clean the list first

Before joining lines, consider whether the source contains:

• leading spaces;
• trailing spaces;
• blank lines;
• duplicates.

Use:

• Trim Whitespace;
• Remove Empty Lines;
• Remove Duplicate Lines.

Then join the cleaned values.

CSV is more complicated than comma joining

A comma-separated string is not automatically valid CSV.

Real CSV fields can contain:

• commas;
• quotation marks;
• line breaks.

Those values require proper CSV quoting rules.

If you are working with structured CSV data, use the CSV Viewer, CSV to JSON, or a proper CSV library rather than manually joining arbitrary fields.

SQL IN clauses

Developers sometimes join IDs to construct a list conceptually similar to:

WHERE id IN (...)

Do not insert untrusted text directly into SQL.

Use parameterized queries or your database library's supported array/list binding.

The SQL Formatter is useful for readability, not for making dynamic string-built SQL safe.

Tags and keywords

A line-based editor is convenient for reviewing a long list of tags or keywords.

After cleanup, converting the list to commas may make it ready for a CMS field.

Check whether the CMS trims values itself and whether commas are allowed inside individual tags.

Environment and configuration values

Some environment variables use comma-separated lists:

ALLOWED_ORIGINS=https://a.example,https://b.example

Before joining URLs, verify the application expects comma-separated text and not JSON.

Use the .env Formatter for the final dotenv syntax.

Shell commands

Lists joined with spaces may be pasted into command-line tools.

Be extremely careful with filenames or values that contain spaces, quotes, wildcards, or shell metacharacters.

A text separator is not shell escaping.

Use the shell's correct quoting and argument mechanisms.

A safe joining workflow

1. Keep a copy of the original list.
2. Trim accidental outer whitespace.
3. Remove unwanted empty rows.
4. Deduplicate if needed.
5. Sort only if order is irrelevant.
6. Choose the destination delimiter.
7. Join the lines.
8. Inspect the final text before use.

Delimiter checklist

Ask:

• Can values contain the delimiter?
• Is this real CSV?
• Does order matter?
• Are duplicates meaningful?
• Does the destination require quoting?
• Is the output going into SQL or a shell?
• Is there a structured format that would be safer?

Joining lines is simple. The important part is understanding how the destination interprets the separator.