Combine, Zip & Split Lists Online

Four ways to combine lists - pick based on what you want in the output:

• Stack - append lists one after another. All of A, then all of B. One long combined list.
• Row Join - merge items at the same position with a separator. Like CONCATENATE across Excel columns: row 1 of A joined to row 1 of B.
• Interleave - alternate items from each list: a1, b1, a2, b2… Great for paired datasets.
• Cartesian - every combination of one item from A with one item from B. 3 items × 4 items = 12 pairs.

Block size N controls how many consecutive lines are taken from each list before switching.

• N=1 (classic zip): a1, b1, a2, b2, a3, b3…
• N=2: a1, a2, b1, b2, a3, a4, b3, b4…
• N=3: a1, a2, a3, b1, b2, b3, a4, a5, a6…

Useful when your data is grouped - for example interleaving name+email pairs so each person’s details stay together.

Cartesian product pairs every item in List A with every item in List B.Good for:

• Generating test data (all size × colour combinations)
• Config matrices (all server × environment pairs)
• Search term combinations (keyword × modifier × location)

Warning: lists grow fast - 1,000 × 1,000 = 1,000,000 pairs. The tool warns you before generating.

Open the Options panel and set Unequal lists:

• Truncate to shortest - stop when the shortest list ends. Clean output with no gaps or padding.
• Fill with value - pad shorter lists with a string you choose. Leave it blank for empty lines, or type N/A to make missing entries explicit.
• Repeat shorter - cycle through the shorter list from the beginning. Useful for applying a repeating label or pattern to a longer list - e.g. alternating “Group A” / “Group B” tags.

When block size is N=1, three output formats are available:

• Flat - one item per line in interleaved order. Best for pasting into other tools.
• Tuples - each pair grouped in parentheses: (apple, cat)
• JSON - each pair as a JSON array: ["apple", "cat"]

For N>1, only Flat is available - block grouping makes the other formats ambiguous.

Use the Split tab at the top of the tool. Three reverse operations are available:

• Split Columns - undoes a Row Join. Paste the joined text, set the same separator, and each column is extracted as a separate list.
• Unshuffle - undoes an Interleave. Paste the interleaved output, set the same N and number of lists, and the originals are reconstructed.
• Unstack - undoes a Stack. Paste the stacked text and split on blank lines (or a custom marker) to separate each sub-list.

Yes - Stack, Row Join, and Interleave support up to 6 lists.

• Click Add List to add a panel (up to 6 total).
• Click the × on any panel to remove it (minimum 2 must remain).

Cartesian is limited to 2 lists. Adding a third makes the output exponential - even 10 items × 10 items × 10 items = 1,000 pairs; 100 items each = 1,000,000. The tool keeps Cartesian at 2 for safety. For set analysis across multiple lists - finding common items or items unique to each list - use Multi-List Compare.

When the two lists would produce more than 5,000 pairs, the tool pauses and shows the expected count instead of generating automatically - to prevent your browser from freezing.

• A warning shows the exact pair count before you commit.
• Click Generate anyway to confirm and proceed.
• The output panel shows up to 2,000 rows. Click Download to get the full result as a text file.

Example: 100 items × 60 items = 6,000 pairs → guard fires and shows “6,000 pairs - click Generate to proceed.”