Duplicate Highlighter for Google Sheets™ finds repeated values and duplicate rows, then highlights them with native conditional-formatting rules without changing, deleting, merging, or rewriting spreadsheet data.

Select a range, choose what counts as a duplicate, preview the matches, and apply a rule that continues working after the sidebar closes.

Highlight duplicate values

Find repeated values within one continuous selected range.

Duplicate values can be compared:

• Independently within each selected column
• Across the entire selected range

Use separate-column comparison for lists such as email addresses, customer IDs, invoice numbers, SKUs, or phone numbers. Use entire-range comparison when duplicates should be detected regardless of which selected cell contains the value.

Highlight duplicate rows

Find complete repeated records using the key columns you choose.

For example, select a customer table and match rows using Email and Company while highlighting the complete selected row. Search and select key columns directly from the sidebar.

Duplicate Highlighter does not remove duplicate rows or change their contents. It adds visual highlighting so you can review the records yourself.

Control what counts as a duplicate

Matching options include:

• Ignore blank cells
• Trim leading and trailing spaces
• Ignore uppercase and lowercase differences
• Highlight every duplicated occurrence
• Highlight only occurrences after the first
• Treat the first selected row as headers

These controls help identify records that look different but should be treated as the same, such as values with extra spaces or inconsistent capitalization.

Choose a highlight color

Apply one of five built-in color presets:

• Yellow
• Red
• Green
• Blue
• Purple

The selected color is applied through a native Google Sheets™ conditional-formatting rule.

Preview before applying

Preview the selected range before making any formatting change. The preview reports the duplicate count and affected groups using the current matching options.

Preview does not change the spreadsheet and does not consume a free apply. You can change the configuration and preview again as often as needed.

For extremely large selections, Preview may be unable to finish within the Google Apps Script execution limit. Apply can still remain available because the native-rule engine does not need to read every selected cell.

Native rules continue working

Duplicate Highlighter creates native conditional-formatting rules in the spreadsheet.

After a rule is applied:

• New matching values highlight automatically.
• A highlight disappears when the value is no longer duplicated.
• The rule continues working after the sidebar closes.
• Existing spreadsheet values remain unchanged.
• No hidden helper sheet or visible helper column is created.

Rules already applied normally remain part of the spreadsheet after the add-on is closed, uninstalled, or a Pro subscription ends.

Quick Apply

For a faster workflow, select a range and choose Highlight Selected Range from the Extensions menu.

Quick Apply uses practical defaults:

• Duplicate values
• Compare each column separately
• Ignore blanks
• Trim leading and trailing spaces
• Ignore uppercase and lowercase differences
• Highlight every duplicate
• Yellow highlighting

A successful Quick Apply counts as one successful apply.

Undo and Clear

Undo removes the exact most recent Duplicate Highlighter rule group when the add-on can verify that the complete rule group is still intact.

Clear this selection removes verified Duplicate Highlighter rules contained within the current selection. The Extensions menu also includes an option to clear verified Duplicate Highlighter rules from the active sheet.

Duplicate Highlighter preserves unrelated conditional formatting and never changes cell values during Undo or Clear.

Preview, Undo, and Clear are free. Undo happens after a successful apply and does not refund or restore a consumed free use.

Large ranges and complete columns

Duplicate Highlighter can apply rules to bounded ranges and complete columns without scanning every cell before creating the rule. Apply has no separate product-defined row limit, but all operations remain subject to Google Sheets™, Google Apps Script, spreadsheet-size, formula, and execution limits.

Selection requirements

Version 1 supports one continuous, unmerged selection in the active spreadsheet.

Unsupported selections include:

• Disconnected multi-range selections
• Selections that intersect merged cells
• Duplicate-row mode without at least one valid key column
• A one-row selection when that row is explicitly excluded as a header

The sidebar explains how to correct an unsupported selection.

Free access

Each Google user receives three lifetime successful applies for Duplicate Highlighter.

The allowance is shared across that user’s spreadsheets and Duplicate Highlighter installations. Creating a new spreadsheet or reinstalling the add-on does not create another allowance.

The third successful apply is allowed. A fourth apply requires Duplicate Highlighter Pro.

Only these successful operations consume an apply:

• Highlight duplicates from the sidebar
• Highlight Selected Range from the Extensions menu

These actions do not consume an apply:

• Opening the sidebar
• Refreshing the selection
• Changing settings
• Previewing matches
• Clearing rules
• Undoing a highlight
• Opening checkout
• Canceled actions
• Validation failures
• System failures
• Safe retries of the same operation

The free allowance is lifetime access and does not reset.

Duplicate Highlighter Pro

Duplicate Highlighter Pro costs $29.99 USD per year.

Pro includes unlimited successful applies for the subscribed Google user, subject to Google Sheets™ and Google Apps Script technical limits.

There is:

• No monthly plan
• No usage-based charge
• No separate per-spreadsheet purchase
• No Stripe trial period

The annual subscription renews automatically each year until canceled.

Billing and cancellation

Checkout and subscription management are hosted by Stripe. Duplicate Highlighter and Codeprint do not receive or store complete payment-card numbers.

Customers can manage their payment method, invoices, renewal, and cancellation through the Stripe Customer Portal opened from the add-on.

Cancellation normally prevents the next annual renewal while Pro remains active through the current paid period. Uninstalling the add-on or revoking Google authorization does not automatically cancel a Stripe subscription.

Applicable taxes, if any, are displayed during checkout. Refund requests are considered individually on a case-by-case basis and are not guaranteed. Applicable statutory cancellation rights are described in the Terms of Service.

Privacy and spreadsheet data

Duplicate matching, previewing, formula generation, and conditional-formatting operations are performed within Google Sheets™ and Google Apps Script.

Duplicate Highlighter does not upload spreadsheet cell values, formulas, sheet names, selected ranges, duplicate groups, or derived duplicate keys to Codeprint.

The external account service processes only the information needed for identity, installation, free-use enforcement, subscription access, billing state, security, and support. This can include:

• Google account identifier and email
• Product and installation identifiers
• Plan and entitlement state
• Successful-apply operation identifiers
• Usage timestamps and outcomes
• Stripe customer and subscription identifiers
• Safe operational and security records

Usage records do not contain spreadsheet values, formulas, sheet names, selected ranges, or duplicate keys.

No AI or machine-learning processing

Duplicate Highlighter does not use artificial intelligence, machine learning, fuzzy matching, model gateways, hosted models, self-hosted models, or offline models.

Google Workspace user data is not transferred to AI providers and is not used to create, train, or improve artificial-intelligence or machine-learning models.

The use of information received from Google Workspace APIs adheres to the Google API Services User Data Policy, including the Limited Use requirements.

Desktop availability

The Duplicate Highlighter sidebar is designed for the desktop version of Google Sheets™. Google does not currently support add-on sidebars on mobile. Native rules already applied to a spreadsheet continue to display and update on supported devices.

Support and policies

Help: https://duplicatehighlighter.com/help
Support: https://duplicatehighlighter.com/support
Privacy Policy: https://duplicatehighlighter.com/privacy
Terms of Service: https://duplicatehighlighter.com/terms
Support email: jacob@codeprint.io

Google Sheets™ is a trademark of Google LLC. Duplicate Highlighter for Google Sheets™ is an independent product operated by Codeprint and is not affiliated with, sponsored by, or endorsed by Google LLC.