Paste Side by Side

Merge two CSV files horizontally by appending columns side by side

Accepted format: CSV (Maximum size: 500 MB)
Accepted format: CSV (Maximum size: 500 MB)

Paste Side by Side

Function

Paste Side by Side combines two CSV files horizontally by placing the columns from the second file directly beside the columns from the first file.

Rows are matched strictly by position. The first row of File 1 aligns with the first row of File 2, the second row aligns with the second row, and so on.

Input Format

  • Input File 1: A CSV file in standard tabular format.
  • Input File 2: A second CSV file, preferably with the same number of rows.

Output Format

  • A combined CSV file containing all columns from both input files.
  • Original row order is preserved.

Applications

  • Combining related datasets.
  • Adding metadata or annotations.
  • Side-by-side comparison of results.
  • Merging outputs from different pipelines.
  • Creating comprehensive reporting tables.

Example

File 1:

Gene,Expression
BRCA1,12
TP53,25


File 2:

Sample,Condition
S1,Control
S2,Treated


Output:

Gene,Expression,Sample,Condition
BRCA1,12,S1,Control
TP53,25,S2,Treated

Unix/Linux Example

paste -d',' file1.csv file2.csv > combined.csv

Python Example

import pandas as pd

df1 = pd.read_csv("file1.csv")
df2 = pd.read_csv("file2.csv")

combined = pd.concat(
    [df1, df2],
    axis=1
)

combined.to_csv(
    "combined.csv",
    index=False
)

Suggested Reading

Important Note: Rows are merged strictly by position and not by a shared identifier or key column. If the two files have different row counts, blank values may appear in the resulting output.