Merge Files
Stack rows from multiple CSV or Excel files into one spreadsheet. Operelio lines up matching columns for you, so you skip the manual copy-paste-align cycle.
By Operelio team
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What it does
Operelio's Merge Files combines multiple spreadsheets into one output file. Think monthly exports stacked into a yearly file, or regional reports rolled up into one master list.
Upload your files. Operelio reads each file's headers, lines up matching columns, and writes a combined output with one header row at the top and every data row stacked underneath. CSV and Excel files can be mixed in the same job.
There's no formula to write and no manual column alignment. The most you'll do is double-check the preview and pick which files to include.
When to use it
Use Merge Files when you have the same type of data split across multiple files and need it in one place.
| Scenario | What it looks like |
|---|---|
| Monthly exports | January.csv + February.csv + March.csv → one yearly file. |
| Regional reports | EMEA.xlsx + APAC.xlsx + Americas.xlsx → one global file. |
| Survey batches | Wave 1 + Wave 2 + Wave 3 of survey responses → one combined file. |
| Vendor data drops | Multiple suppliers each sending the same template → one stacked file. |
How to use it
Upload your files
Drop two or more files into the upload area. CSV or Excel both work, and you can mix them. Pro allows up to 10 files per job; Team up to 15; Agency up to 25.
Check the preview
Before you run, Operelio shows a quick preview: total rows, total columns, and a heads-up if any file's columns are different from the others. The preview is your chance to catch a wrong file or a header drift before spending a job credit.
Adjust if needed
If the preview shows drift you didn't expect, remove or re-upload files. If the drift is fine and you want Operelio to fill the gaps with blanks, leave it as-is.
Click Run
Operelio combines the files quickly and gives you a download. The output is a single XLSX spreadsheet with one header row and all your data rows underneath, up to your plan's row limit (50,000 on Pro, 75,000 on Team, 150,000 on Agency).
Run Clean Headers on each file first if your headers are even slightly inconsistent. Mixed cases ("Email" vs "email") and stray spaces are the single most common cause of unexpected column drift in Merge.
How header matching works
Operelio matches columns by exact header name. Matching is case-sensitive and whitespace-sensitive, so "Email", "email", and "Email " (with a trailing space) all become separate columns in the output. To merge them into one column, run Clean Headers on each file first: it lowercases every header and trims spacing so the merge lines them up correctly.
Headers from the first file in your list set the column order, and that file names the output. New headers from later files are added to the end of the column list. Row values are matched to the right column by their header name, and missing values are left blank. You can reorder the files with the arrows on each file card before running.
For Excel files with several sheets, Operelio reads the sheet that was active when the file was saved.
What happens when columns don't match
Operelio doesn't refuse to merge files with different columns. It does its best with what's there, then tells you what was different. Here's exactly what happens in each case:
| Situation | What Operelio does |
|---|---|
| A column is in some files but not others | The column is added to the output. Files that had the column keep their values; files that didn't get blank cells in that column. |
| A file has a typo in a header ("Emial" vs "Email") | Treated as two separate columns. Run Clean Headers first or fix the typo in the source file. |
| A file is empty (zero rows AND zero headers) | Skipped with a warning. It doesn't count toward the merged total. |
| A file has zero data rows but valid headers | Included. Its headers join the unified set; it just contributes no rows. |
| A file repeats the same header name twice | Only the last column with that name is kept, and the results page shows a warning naming the file and header. Run Clean Headers on the file first to keep both. |
| The combined files exceed your plan's row cap | Operelio writes the rows that fit and shows a row-limit banner on the results page with what was processed and what was skipped. |
Plans and limits
Merge Files is a Pro feature. There's no free tier; all three plans get the full feature set and differ only in scale.
| Limit | Pro | Team | Agency |
|---|---|---|---|
| Files per merge | 10 | 15 | 25 |
| File size | 25 MB each | 35 MB each | 100 MB each |
| Rows in merged output | 50,000 | 75,000 | 150,000 |
| Output format | XLSX | XLSX | XLSX |
| Price | $39/month, or $351/year (effective $29.25/month, 25% off) | $99/month, or $891/year (effective $74.25/month, 25% off) | $299/month, or $2,691/year (effective $224.25/month, 25% off) |
What the results show
After the job runs, the results page summarizes the merge with a sentence like "Combined 3 files into 5 rows across 5 columns." Below that you'll see the key numbers and the per-file breakdown.
| What you'll see | What it means |
|---|---|
| Files merged | Number of non-empty files that were combined. |
| Total rows | Number of data rows in the merged output (one header row sits above them, not counted here). |
| Columns | Number of unique columns across all input files. |
| Warnings | Number of notes about the merge: column drift (extra or missing columns), empty files skipped, and repeated header names within one file. |
| Per-file table | Each filename and its row count, so you can verify each file contributed what you expected. |
| Warnings panel | Plain-English notes about each file's drift, like "march-leads.csv has 1 extra column: source. Added to output." |
| Preview | First few rows of the merged output, so you can sanity-check the alignment before downloading. |
Frequently asked questions
What happens to empty files?
Empty files (zero rows and zero headers) are skipped with a warning and don't count toward the merged total. A file with valid headers but zero data rows is included: its headers join the unified set, it just contributes no rows.
Can I merge the tabs of one workbook instead of separate files?
Yes. Upload the single workbook and Merge offers to combine its tabs into one list instead of asking for a second file, with an optional Source Tab column recording which tab each row came from. When you are merging separate files, each file card has its own tab picker, so every workbook contributes exactly the tab you choose. See the multi-tab workbooks guide for the full picture.
Can I mix CSV and Excel files?
Yes. Operelio reads both formats and combines everything into one spreadsheet. The output is a single XLSX file on every plan that can run Merge.
What plan do I need?
Merge Files needs Pro (10 files per job), Team (15 files per job), or Agency (25 files per job). Pro is $39/month, or $351/year if you pay annually (25% off, equivalent to $29.25/month). Team is $99/month, or $891/year on annual billing. Agency is $299/month, or $2,691/year on annual billing. Operelio's other 12 tools (Clean Headers, Deduplicate, Match & pull columns, Compare Files, and eight more) are free to use.
Does the column order matter?
No. Columns are matched by name, not position. Your files can have columns in any order, and Operelio will line them up by header name.
What if my files use "Email" in one and "email" in another?
Header matching is strict: "Email", "email", and "Email " (with a trailing space) all become separate columns. Run Clean Headers on each file first to lowercase and trim every header, then the merge will line them up correctly.
What's the row limit on the merged output?
Pro processes up to 50,000 rows per job; Team up to 75,000; Agency up to 150,000. If your combined files go over the cap, Operelio writes the rows that fit and shows a banner on the results page with the total, what was processed, and what was skipped.
Can I merge more than 25 files at once?
Not in a single Merge job. To combine more than 25 files, run Merge twice: combine the first batch into one file, then merge that output with your remaining files in a second job.
What if I make a mistake?
Nothing to undo. Your original files are kept untouched: a merge just produces a new file. If you don't like the result, run the job again with different files or settings.
Ready to get started?
Upload a file and run your first transformation. Free, no credit card required.