Replacing a Constant Across Many Files

Over time, websites and applications evolve. Domains change, systems migrate, APIs update, brands re-name, and configuration values get replaced. When that happens, one small piece of text — like a domain name, identifier, or constant — may suddenly need to be updated in dozens or even hundreds of files. Doing that manually is slow, frustrating, and risky. The more times you edit something by hand, the more likely you are to make a mistake or miss something entirely.

Bulk replacement solves that problem. When handled correctly, it allows you to update large numbers of files quickly, consistently, and safely, without hunting through every folder and line of code. The goal isn’t just to “run a command,” but to do it confidently, with preparation, verification, and care for your project.

This guide explains how to replace a constant — or any repeated value — across multiple files in a controlled and professional way. It includes options for both Windows and macOS/Linux, written in clear language so it’s understandable for everyday users and still trusted by technical professionals.

Before You Start: Safe and Smart Bulk Editing

Bulk editing is powerful. A single command can change hundreds of files instantly. That’s a benefit — but it also means planning ahead matters.

1️⃣ Create a Backup First

Before you modify anything, make sure you can undo it easily. You can:

• make a quick copy of the folder
• zip the project
• or commit your files to Git

If anything unexpected happens, restoring should be stress-free.

2️⃣ Know What You’re Changing

Even text that looks similar can actually be different. For example:

abc.com

www.abc.com

api.abc.com

Those are not interchangeable. Before replacing, it’s best to search for the value first, review where it appears, and confirm you truly want it changed in every location.

3️⃣ Only Replace in Text Files

Bulk replacement tools will happily modify anything — even files that shouldn’t be touched.
Stick to text-based files such as:

• .html, .css, .js
• .php, .json, .txt
• .md, .yml, .xml

Avoid binary files like images, videos, PDFs, or compiled or executable files

Those can break instantly if modified.

4️⃣ If Unsure, Test on a Small Copy First

If this is your first time or you’re working on something important, do a small trial run in a duplicated folder. Once you see everything works smoothly, apply it to your real project.

Replacing Text Across Many Files on Windows (PowerShell)

Windows includes PowerShell, which is excellent for this type of task.

Step 1: Open Your Project Folder

Open PowerShell and move into the folder you want to modify. For example:

cd "$env:USERPROFILE\Downloads\myproject"

Step 2: Search First (No Changes Yet)

This shows every location where abc.com exists:

Select-String -Pattern "abc.com" -Recurse -Include .html,.css,.js,.php,.json,.txt

If results appear, review a few to confirm they’re expected.
If nothing appears, there’s nothing to replace.

The . simply tells PowerShell to treat the dot as a literal dot, not a special character.

Step 3: Replace It Everywhere

Once confident, run the replacement:

Get-ChildItem -Recurse -File -Include .html,.css,.js,.php,.json,.txt |
ForEach-Object {
(Get-Content $_.FullName -Raw) -replace "abc.com","xyz.com" |
Set-Content $_.FullName -Encoding utf8
}

This finds all matching files, opens them, replaces every instance of the text, and saves them back safely.

Step 4: Verify

Double-check that nothing remains:

Select-String -Pattern "abc.com" -Recurse

If no results appear, the update succeeded.

Replacing Text Across Many Files on macOS & Linux

On macOS and Linux, you can do the same thing using Terminal with find and sed.

Step 1: Go to Your Project Folder

cd ~/Downloads/myproject

Step 2: Run the Replace Command

macOS

find . -type f ( -name ".html" -o -name ".css" -o -name ".js" -o -name ".php" -o -name ".json" -o -name ".txt" ) \
-exec sed -i '' 's/abc.com/xyz.com/g' {} +

Linux

find . -type f ( -name ".html" -o -name ".css" -o -name ".js" -o -name ".php" -o -name ".json" -o -name ".txt" ) \
-exec sed -i 's/abc.com/xyz.com/g' {} +

This scans all matching files, replaces all text, and saves changes automatically

Optional Safety on macOS/Linux

If you want sed to automatically create backups:

sed -i.bak 's/abc.com/xyz.com/g' file.ext

You’ll get:

• file.ext (updated)
• file.ext.bak (backup)

Helpful Related File Tasks

Once you’re comfortable with bulk editing, a few other file management tools become extremely helpful.

🔍 Find All Files That Contain Text

PowerShell:

Select-String -Pattern "something" -Recurse

macOS/Linux:

grep -R "something" .

🏷️ Bulk Rename File Extensions

PowerShell:

Get-ChildItem -Recurse -Filter *.htm |
Rename-Item -NewName { $_.BaseName + ".html" }

macOS/Linux:

for f in *.htm; do mv "$f" "${f%.htm}.html"; done

📏 Identify Large Files Quickly

PowerShell:

Get-ChildItem -Recurse -File |
Sort-Object Length -Descending |
Select-Object -First 20 Name, Length

macOS/Linux:

find . -type f -printf '%s %p\n' | sort -nr | head -20

Updating a constant across many files doesn’t have to be stressful. With the right approach, it becomes a quick, reliable, and well-controlled process instead of a tedious manual chore. A little preparation, a quick backup, and thoughtful verification ensure that your changes apply consistently — without surprises.

Handled correctly, what once took hours can now be completed confidently in seconds.

If you ever need assistance planning or performing bulk updates, reviewing results, or ensuring everything works smoothly afterward, professional help is always available — and can save both time and frustration.