Merge Two Lists

How to use

1. 1Paste your first list into List A and your second list into List B, one item per line, or load the sample to see how the pairing works.
2. 2If your lists are not one item per line, change Split each list by to commas, tabs, whitespace, or a custom delimiter.
3. 3Choose a layout: Side by side pairs A and B on one line, while Interleave alternates the two lists item by item.
4. 4For side by side, pick the separator that goes between each A and B value, such as a space, comma plus space, equals sign, or a custom string.
5. 5Decide what happens when the lists are different lengths: keep every row with a fill value for the gaps, or stop at the shorter list.
6. 6Read the merged result, then use Copy result or Download .txt. Use Swap A and B to flip the order. Everything stays in your browser.

About this tool

Merge Two Lists takes two separate lists and combines them by position into a single output, which is the everyday spreadsheet move of putting one column next to another and the same idea as the zip function in Python. It is the positional counterpart to a set comparison: instead of asking whether a value is a member of each list, it pairs item 1 of list A with item 1 of list B, item 2 with item 2, and so on, so order is what matters. That makes it the right tool whenever you have two parallel lists that belong together but live in different columns or different files. The two layouts cover the cases people actually need. Side by side joins each pair onto one line with a separator you choose, which is how you turn a list of first names and a list of last names into full names, build host=value configuration lines from a keys list and a values list, pair link text with URLs, or stitch two parallel CSV columns back into one row. Interleave alternates the lists item by item, producing list A item one, list B item one, list A item two, and so on, which is the way to weave two ordered sequences back into a single stream. Because real lists are rarely the same length, uneven inputs are handled explicitly rather than silently truncated: keep every row and fill the missing slots with a placeholder you set, such as N/A or a blank, or stop at the length of the shorter list so no half-empty rows are produced. The splitter understands the formats lists arrive in, so each side can be broken on new lines, commas, semicolons, tabs, any run of whitespace, or a custom delimiter, and you can choose how the finished rows are separated, whether one pair per line for pasting into a column or comma separated for a single cell. The separator placed between the two values in side by side mode is yours to pick from common choices like a space, comma, comma plus space, pipe, dash, arrow, or equals sign, or any custom string. Two cleanup toggles keep the pairing honest: trimming removes stray spaces around each item, and skipping blank items drops empty lines so a single missing entry does not shift every pair below it out of alignment. A live count shows how many items each list holds, how many pairs or items came out, and the size of any length gap, and a notice tells you exactly how an uneven pair of lists was resolved. You can swap the two lists with one button, copy the result, or download it as a plain text file. Everything runs in your browser. The lists you paste are never uploaded, logged, or stored.

Free to use. Works in your browser. No signup, no login.