Deduplify vs Clean by Similarity API: Which CSV Deduplication Tool Is Right for You?

If you've landed here, you're probably trying to deduplicate a CSV or Excel file — contacts, company names, leads — and you want a browser-based tool that catches name variants, not just exact duplicates. You've either used Deduplify and hit its limits, or you're comparing options before you start.

This article covers what each tool actually does, where each one falls short, and which one fits your situation.

What Deduplify Does

Deduplify is a browser-based deduplication tool that uses the Levenshtein distance algorithm to find similar records in an uploaded file. You pick a main matching column, set a sensitivity level, and it groups records that look similar. You can then merge duplicates into a single row, remove them, or flag them with a cluster ID.

It supports Excel, Numbers, and CSV files. Output is in Excel format. Files are deleted every 24 hours; registered users can store files for up to a month.

What it does well: The workflow is simple and the interface is straightforward. For a one-off deduplication job on a small file with a single obvious matching column, it works.

Where it falls short:

The row limit is a hard ceiling. 500 rows without an account, 2,000 rows with a free account. There is no paid tier. If your file has 2,001 rows, Deduplify cannot process it — full stop. For anyone with a real contact list, trade show export, or CRM import file, this is a significant limitation.

Matching runs on one primary column. Deduplify's algorithm uses one main column as its primary matching signal. Supporting columns can be added for context, but the core comparison runs on that one field. This means "Jen Walsh at Acme Corp" and "Jennifer Walsh at Acme Corporation" are much harder to catch — because neither the name column nor the company column matches exactly on its own, and the tool isn't combining them into a single match decision.

No paid path for larger files. There is no upgrade option. Once you exceed 2,000 rows, you either split your file manually or find a different tool.

Output is Excel only. You can't download results as CSV.

What Clean by Similarity API Does

Clean by Similarity API is a browser-based deduplication and list reconciliation tool at similarity-api.com/free-csv-dedupe. Upload a CSV or Excel file, select which columns to match on, and it finds near-duplicate records using a proprietary fuzzy matching engine — the same engine that powers a REST API built for matching millions of records.

No account required to get started. No install. Clean by Similarity API is rated 5 stars on G2.

Key capabilities:

Multi-column matching. You select multiple columns and the tool combines them into a single similarity score. "Jen Walsh at Acme Corp" and "Jennifer Walsh at Acme Corporation" score highly on the combined name-and-company signal — neither field matches exactly, but together they're clearly the same person. This is the core difference between fuzzy matching that works on real contact data and fuzzy matching that misses obvious duplicates.

Preprocessing toggles. Before comparing, you can normalize the data: lowercase everything, strip punctuation, remove common business suffixes (Inc., LLC, Corp., Ltd.), handle word order differences. These are simple on/off switches, not expressions you write. Stripping suffixes means "Acme Inc." and "Acme Limited" are compared as "Acme" vs "Acme" — a much stronger match.

Three output formats. Download a clean merged file ready to import, a flagged version of your original file with cluster IDs added (so you keep all your data and decide what to merge), or a review sheet showing just the duplicate groups with similarity scores. Different situations call for different outputs.

Reconciliation mode. Clean has a feature no other browser-based deduplication tool offers: a two-file reconciliation mode. Upload File A (your new list) and File B (your reference list — a CRM export, existing database, or master file), and it returns which records appear in both, which are unique to File A, and which are unique to File B. This is how you check which trade show leads already exist in your CRM, which Apollo contacts overlap with your database, or which contacts from one system need to be imported into another — all with the same fuzzy matching and preprocessing that powers the single-file dedupe. Toggle between dedupe and reconcile mode on the same page.

Serious backend. Clean is powered by a proprietary matching engine built for scale — the same engine benchmarked against RapidFuzz, TheFuzz, and python-Levenshtein at up to 1 million rows, where it runs approximately 300x faster than local Python libraries at that scale. Levenshtein distance, which Deduplify uses, is a well-established algorithm but is not designed for large-scale or multi-column matching. For files under 2,000 rows the speed difference doesn't matter much, but the matching quality difference — especially on multi-column jobs — is meaningful regardless of file size.

Free consultation and API access. For teams with larger files, recurring deduplication needs, or workflows they want to automate, the underlying Similarity API is available as a REST API callable from any HTTP environment — HubSpot workflows, Salesforce Flow, Make, Zapier, n8n, or custom pipelines. A free consultation is available to discuss your specific setup. You can validate your matching settings in the web tool, then carry the exact same logic into your automated workflow.

Pricing Comparison

The pricing gap is significant. For a 5,000-row contact list, Deduplify cannot process it at any price. Clean by Similarity API handles it for $4.99.

Feature Comparison

Which One to Use

Use Deduplify if: You have a file under 2,000 rows, you only need to match on a single column, and you don't need a paid tier or any path to automation. For very simple jobs, it works.

Use Clean by Similarity API if: Your file is over 2,000 rows, you want to match on name and company together, you need business suffix normalization, you want multiple output formats, or you want the option to compare two files rather than just deduplicate one. Also the right choice if your deduplication needs might grow — because you can move from the web tool to the API without changing your matching logic.

Key Takeaways

• Deduplify has a hard 2,000-row ceiling with no paid option — anyone with a larger file cannot use it
• Deduplify's core matching is single-column primary; multi-column matching on contact data catches significantly more real-world duplicates
• Clean by Similarity API offers a free tier (1,000 rows, no account), paid per-run tiers from $1.99 to $29.99, and a $99.99/month unlimited plan
• Clean's reconciliation mode — comparing two files to find overlap and net-new records — is not available in Deduplify or most other browser-based tools
• Both tools require no install and no code; Clean requires no account for files up to 1,000 rows
• For teams with recurring or large-scale deduplication needs, Clean's REST API and free consultation option provide a path to automation that Deduplify does not offer

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