Validate and clean email addresses in a CSV
Before you import a list into your CRM or email platform, upload it here. SpreadsheetFix trims and lowercases every address, then moves rows with malformed emails into a separate quarantine so they don’t pollute your import.
Free up to 5,000 rows · No sign-up · Nothing uploaded
Drag & drop your file
or click to browse — CSV, TSV, XLSX up to 50MB
Before and after
email,first_name Sam@Example.COM ,Sam lee@example,Lee kim@example.org,Kim sam@example.com,Sam
email,first_name sam@example.com,Sam kim@example.org,Kim # quarantined: lee@example (no domain suffix) # 1 duplicate removed
How it works
- 1
Upload the contact list as CSV or Excel. SpreadsheetFix detects email columns automatically.
- 2
Addresses are trimmed and lowercased so duplicates match, then checked for a valid format.
- 3
Rows with invalid emails move to quarantine for review; download the clean list.
What counts as invalid
SpreadsheetFix checks syntax: a local part, a single @, a domain and a top-level domain of at least two letters. That catches typos like “lee@example”, “ana.gmail.com” and stray characters from copy-paste. It does not contact mail servers, so it won’t tell you whether a mailbox exists — that also means no address ever leaves your machine.
Quarantine instead of delete
Invalid rows aren’t silently thrown away. They’re set aside in a quarantine list so you can fix a typo and keep the contact, or confirm the row should go.
Lowercase first, then de-duplicate
“Sam@Example.COM” and “sam@example.com” are the same inbox. Normalising case before de-duplication stops the same person being imported twice and receiving every campaign twice.
Frequently asked questions
How do I check if emails in a CSV are valid?
Upload the CSV above. SpreadsheetFix flags every address with an invalid format and moves those rows to a quarantine list you can review before downloading.
Does SpreadsheetFix verify that the mailbox exists?
No. It validates format only and never contacts mail servers, which keeps your list private. Use it to remove malformed addresses before running a deliverability check.
Will it remove duplicate emails?
Yes. Emails are trimmed and lowercased first, then duplicate rows are removed, so differently-capitalised copies of the same address are caught.
Is it safe to upload customer emails?
Your file is never uploaded. All checks run in your browser, which makes SpreadsheetFix suitable for GDPR-sensitive contact lists.
How many emails can I validate for free?
Up to 5,000 rows per file on the free plan, or 500,000 rows with Pro.
Cleaning bigger files every week?
Pro cleans up to 500,000 rows per file, unlocks all 18 rules, exports to Excel and removes the watermark.
See Pro pricingRelated tools
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