Import CSV MCC : migrer 1000 comics depuis Excel 2026

Any collector who has held an Excel or Google Sheets for three years knows the feeling: the sheet becomes slow, the tabs multiply, the formulas break as soon as you add a column. At 1,000 lines, the spreadsheet is no longer enough, and the migration to a dedicated application like My Comics Collection (MCC) automatically becomes more profitable. This migration must still not break three years of patient input. This is the whole point of a well-prepared CSV import: keep the raw data, gain the enriched data (covers, creators, live rating) and not lose any line along the way.

This guide breaks down the complete process for 2026: why a spreadsheet caps at 500-700 entries before becoming a chore, what CSV structure MCC expects exactly, how to prepare its Excel or Google Sheets export without surprises, how to control column mapping in the MCC UI, how automatic deduplication works on the serial+number+variant key, how to read and correct rejected rows, and how to check the integrity of the result on a random sample. A practical case timed on 1,000 comics closes the question.

Why migrate your Excel to MCC in 2026 (spreadsheet limits to 500+ comics)

The spreadsheet is the default tool for almost every starting collector. It's free, familiar, open on all devices, and zero friction at launch. The problem doesn't appear until 200 comics. It becomes visible around 500. It becomes unbearable beyond 700. Three mechanics explain this ceiling.

The first mechanism istyping fatigue. On a spreadsheet, each comic added requires manually filling in 8 to 12 columns: series, number, publisher, publication date, creators, condition, price paid, purchase date, source, storage location, current value, notes. At 30 seconds per line (expert pace), that's 5 hours of crisp typing for 600 entries. At 60 seconds per line (realistic pacing with publisher and date lookups), it's 10 hours. And each editor or series spelling correction propagates the error over hundreds of lines that nothing automatically harmonizes. The articlecatalog your comics online: app vs spreadsheetprecisely figures this difference in input time between the two families of tools.

The second mechanism isloss of consistency. On Google Sheets or Excel, nothing stops a user from typing "Marvel", "marvel", "Marvel Comics", "Marvel comics" or "MAR" in the publisher column. After three years of discontinuous entry, we find five to eight variants for the same label. Sorting and filters become unreliable, statistics by publisher are false, and a “cleaning” day must be planned every six months. No native validation locks the input in the expected format, unless you set up a Data Validation system using a drop-down menu which itself requires an hour of configuration and which breaks on the first pasting of external data.

The third mechanism isloss of value. A spreadsheet knows nothing about the current rating of your comics. The Current_Value column is entered manually, dated six months ago, and does not reflect the 2026 market. For a collection with an investment dimension, this is unacceptable. The catch-up solutions (diverted GOOGLEFINANCE function, AppScript scripts, Zapier integrations) all require technical skills that the majority of collectors do not want to acquire. A dedicated application includes the native live rating, recalculated every week on comparable eBay sold listings.

The practical verdict: a spreadsheet is excellent up to 300 comics, manageable up to 500, painful between 500 and 1,000, and frankly counterproductive beyond that. At 1,000 comics, the migration to MCC pays for itself in a few months thanks to the saving in entry time and the regained reliability of the data. The condition is to successfully import without losing the history.

Expected MCC CSV structure (12 columns Issue/Number/Grade/Purchase/...)

The MCC import screen accepts a CSV or XLSX file as input and recognizes twelve main columns. Knowing this target schema in advance allows you to prepare your Excel export so that it pastes directly, without renaming each header by hand during mapping. The rule is simple: the more your CSV resembles the target schema, the faster and more reliable the import.

Three columns are strictly mandatory: Series, Number and at least one state (State or CGC_grade). The other columns are optional and can be completed later from the MCC interface. If a mandatory column is empty on a line, this line will be rejected on import and listed in the error report. It is therefore better to check the completeness of critical columns before uploading rather than having to correct line by line after the fact.

The date format deserves special attention. Excel and Google Sheets store dates in different regional formats (03/15/2025 in FR, 3/15/2025 in US, 2025-03-15 in ISO). MCC accepts three formats for import: ISO YYYY-MM-DD (recommended), DD/MM/YYYY (explicit French format), and a month-year text format (March 2025) which will be converted to the first date of the month. Any other form generates an error or worse, a silent misinterpretation. The most relevant practice is to reformat all date columns in ISO before CSV export, via a function TEXT(A1,"yyyy-mm-dd") on Sheets or =TEXTE(A1;"yyyy-mm-dd") on French Excel.

The monetary columns require the same rigor. MCC expects a decimal number with a dot separator (12.50), not a comma (12.50), and without a currency symbol. The thousands separator (1,250.00 or 1,250.00) must be removed before export. This is the most frequent error on a French Excel export, which produces "€1,250.50" and systematically crashes the MCC parsing. The CNUM or VALUE function on Excel and VALUE on Sheets cleanly converts to a usable number.

Prepare your Excel/Google Sheets export

The quality of the import depends 80% on the quality of the source file. Five preparation steps minimize post-import remedial work.

Step 1:audit your existing spreadsheet. Open your main sheet and count the number of true lines (without headers, without separator lines, without automatic totals). If you have several tabs (for example one tab per publisher or per year), list them. Decide in advance whether you import everything at once (recommended) or in batches (useful beyond 3,000 entries to limit the risk in the event of an error). Out of 1,000 comics, a single import is more than manageable. The articleinventory 1,000 comics in 90 minutes: bulk methodgives the general methodological framework for any volume treatment.

Step 2:harmonize the wordings. This is the most time-consuming step but the most profitable. Filters the Editor column on all distinct values ​​(Data → Filter → Select unique values ​​on Excel, or Data → Create filter then click the arrow on Sheets). You often discover 5 to 10 variants for the same publisher ("Marvel", "Marvel Comics", "MAR", "M"). Choose a canonical form (Marvel) and use Find-Replace to harmonize. Repeat the operation for the Series column, where spelling variations are common (Amazing Spider-Man / The Amazing Spider-Man / Amazing SpiderMan). This harmonization takes 20 to 40 minutes on 1,000 rows but it avoids hundreds of post-import deduplication errors.

Step 3:rename columns. Align the headers of your spreadsheet with the 12-column MCC diagram described above. This is optional (manual mapping does the job) but it speeds up the mapping and reduces the risk of error. If you have a "Quote" column that corresponds to "Current_Value" and a "Cost" column that corresponds to "Pay_Price", clarify these correspondences before exporting. Removes or renames ambiguous columns ("Info", "Miscellaneous", "Other") that map to nothing.

Step 4:convert formats. Reformats all date columns to ISO YYYY-MM-DD via a TEXT formula. Convert all amounts to decimal number with separator point. Check the Grade column: if you mixed CGC grades (9.8) and text notes (NM), split it into two columns State and CGC_grade. Non-slabbed comics have a text rating (NM, VF, etc.), slabbed comics have a digital CGC rating. Mixing the two in a single column systematically generates mapping errors.

Step 5:export to CSV UTF-8. In Excel, File → Save As → CSV UTF-8 (comma delimited) (*.csv). On Google Sheets, File → Upload → Comma Separated Values ​​(.csv). UTF-8 encoding is mandatory: without it, French accents (é, è, à, ç) become corrupted characters on import (é, è). The .xlsx extension also works but CSV is more predictable and lighter. For recurring export workflows, the articleexport CSV comics collection: how to do itdetails the pitfalls and encoding options depending on the source software.

Upload + mapping UI MCC columns

The MCC import screen can be found in the app under Settings → Import Collection. The interface accepts a file dragged and dropped or selected from the file browser. The maximum size is 25 MB, which corresponds approximately to 50,000 lines without images. For 1,000 comics without images, the file weighs 100 to 200 kb, so well below the limit.

Once the file has been uploaded, MCC browses the CSV and offers a mapping screen. The left column lists the headers detected in your file (Series, Number, Flight, Rating, State, Price_pay, etc.). The right column lists the 12 fields of the MCC schema. You drag each source header to the corresponding target field, or you select the target field from a drop-down menu. MCC automatically suggests obvious mappings (Series → Series, Number → Number) and leaves ambiguous columns waiting.

The classic mapping trap is to confuse publication_date (date when the publisher released the comic) and purchase_date (date when you acquired it). The two dates often exist in the source table but with unclear names ("Date 1", "Date 2"). Check each date mapping rather than clicking quickly: an inversion produces 1,000 comics displayed as "acquired in 1968" or "published in 2024", an error which requires a massive post-import correction.

The second pitfall concerns the Variant column. If your source spreadsheet does not distinguish between variants (you have only one row per number), leave the Variant field unmapped: MCC considers by default that each row is a Regular cover. If you distinguish between variants (one line for each cover A, B, C), map Variant to the corresponding field. Bad mapping here produces either phantom duplicates (two Amazing Spider-Man #800 lines merged into one) or broken unifieds (a B cover treated like a Regular cover).

Once the mapping is validated, MCC offers an overview of the first 10 lines: it displays how each line will be imported, with any transformations (reformatted dates, converted amounts). Read this overview carefully before clicking "Start import". If a transformation seems strange to you (an amount that goes from 12.50 to 1250, a date that goes from 2024 to 2099), it is because a mapping or format is misinterpreted. Better to correct now than undo 1,000 bad imports.

The import itself takes 30-90 seconds for 1000 rows depending on the connection. A progress bar displays the percentage processed. At the end, MCC displays a summary: N lines imported successfully, N duplicate lines merged, N lines rejected with errors. Keep this page open: it is what controls the rest of the process.

Automatic deduplication (serial key+number+variant)

MCC deduplication is the most time-saving feature in the long run. It avoids having two Amazing Spider-Man #800 files in the database because it was imported twice (export in May, re-export in June), or because two physical copies are entered under slightly different labels.

The MCC deduplication key combines three fields:Series(standardized: standardized case, “The” articles deleted at the beginning, standardized spaces) +Number(normalized: leading zeros removed, #001 and #1 considered identical) +Variant(normalized: Regular and empty considered identical, A and Cover A identical). This triple key fixes 95% of cases. For the remaining 5% (variants of variants, special editions), manual intervention remains necessary.

Concretely, on import, MCC goes through each line and compares it to the existing database. Three outcomes are possible.Case 1: the line does not exist in the database, it is created as a new record.Case 2: the line already exists with exactly the same serial+number+variant key, MCC offers two options depending on the setting: overwrite the existing data with the new ones, or keep the old ones and ignore the new ones.Case 3: the line looks like an existing one without an exact match (e.g. "Amazing Spider-Man #1" and "Amazing Spider-Man Vol 1 #1"), MCC marks the line as "to check" and lets you arbitrate manually after import.

Managing multiple copies is a special case. If you own two copies of Amazing Spider-Man #1 (a CGC 9.4 slab and a French reading copy), you want two separate records in MCC, not a merger. The triple key is not enough (both lines have series=Amazing Spider-Man, number=1, variant=Regular). The solution consists of adding a Copy field (numbered 1 and 2) in your source CSV: MCC recognizes this field and creates two separate files linked to the same issue. For collectors who systematically have several copies, the articleimport your comics collection into an applicationdetails the multi-exemplar pattern.

Line error management (rejected lines + correction)

No import on 1000 lines goes to 100%. Expecting 2 to 5% of rejected lines is realistic. Out of 1,000 entries, that's 20 to 50 lines to correct manually. The MCC error report lists each rejected row with the reason. Understanding these patterns speeds up the correction.

THEformat errorsare the most common. A poorly formatted date (03/15/2025 while MCC was waiting for ISO), an amount with comma instead of point (12.50 instead of 12.50), a CGC grade in text format ("9.8" instead of 9.8). MCC displays the received value and the expected format, making correction trivial. The simplest is to correct directly in the source CSV and re-run a partial import on these lines only.

THEreference errorsappear when MCC does not recognize the specified series. If you typed "Amasing Spider-Man" (typo) or "ASM" (abbreviation), MCC does not find the series in its internal database and rejects the line. Two solutions: correct the spelling in the source CSV, or manually create the serial file in MCC then restart the import. For uncommon indie or independent comics, the second option is often necessary because the MCC database does not cover the entire world production.

THEconsistency errorsare the most subtle. You indicated a CGC grade on a line without having specified that the comic is slabbed, or a text state (NM) with a CGC_cert indicated, which is contradictory. MCC points out these inconsistencies and asks you to arbitrate: slab or raw, your choice. Out of 1,000 lines entered over three years with evolving conventions, this type of error often represents half of the rejections.

THEduplicate errors rejectedappear when strict mode blocks a line that is too similar to an existing one without being identical. MCC lists the two lines side by side and asks you to choose: merge (the two become a single file for which you choose the priority fields), keep both (creation of two separate files), ignore the new one (the CSV line is left aside). This is the step that requires the most human judgment and that no algorithm can completely automate.

Good practice: don't correct errors one by one in the MCC interface, it's slower. Download the error report in CSV, correct everything in Excel or Sheets, and rerun a partial import containing only the corrected lines. On 50 errors, the time saving is 70 to 80% compared to a single correction in the app.

Post-import check 50 random lines

The mistake after a migration of 1,000 comics is to consider the import complete as soon as the progress bar reaches 100%. Post-import verification is non-negotiable: without it, silent errors are discovered weeks or months later, when it is too late to relate them to a reliable prior state.

The 50 random lines method is fast and statistically valid. Out of 1,000 imports, checking 50 lines (5%) gives a margin of error of around ±3%, which is more than enough to detect systemic problems. Drawing these 50 lines truly at random requires discipline: not only selecting the first lines (often the best entered, therefore bias), nor the last (often the most recent, therefore still in memory). The RAND or ALEA function on Sheets and Excel allows you to generate 50 random indices between 1 and 1000, then open each corresponding row in MCC.

For each sampled line, check four points:series and number(the two primary keys, which must never be incorrect),the date of publication(check on ComicVine or League of Comic Geeks that the date displayed in MCC corresponds to the real one),the price paid and the value(make sure that no misinterpreted comma has transformed 12.50 into 1250 or vice versa),the variant and the grade(checks that a variant cover has not been lost in Regular and that a CGC grade is in slabbed mode and not in raw).

The verification time is short: 30 to 60 seconds per line, or 25 to 50 minutes for 50 lines. This is negligible compared to the total migration time, but it is what makes the difference between a clean import and a shaky import which poisons the database for years. If more than 3 errors appear on 50 lines (rate > 6%), it means that a mapping or format is systematically wrong. It is then better to cancel the bulk import (the MCC interface offers a "rollback" within 24 hours following the import) and start again after correcting the root cause.

Beyond the random sample, a global check on the aggregates is useful. Count the total number of records imported into MCC and compare it to the number of lines in the source CSV: a difference of more than 5% indicates a deduplication problem. Calculate the sum of Price_pays in MCC and compare it to the sum in your original spreadsheet: a significant difference indicates a monetary format problem. Count the number of distinct publishers in MCC and compare it to your spreadsheet: a discrepancy indicates poor harmonization of labels upstream. These three global checks take ten minutes and detect 80% of systemic errors.

To anchor the security of this migration, immediately export a CSV backup from MCC after verification and store it according to the 3-2-1 rule: 3 copies, 2 different media, 1 off-site. The articlebackup cloud comics: 3-2-1 ruleapplies this principle to a digital collection. Having a post-import backup prevents you from losing everything if you mishandle MCC in the days that follow.

Practical case 1000 comics Sheets vs timed MCC migration

To make the benefit of the migration concrete, here is a practical case timed on a real collection of 1,000 comics managed for four years on Google Sheets, then migrated to MCC. Times are measured with a stopwatch on a representative sample.

Phase 1: audit of the source Sheets.15 minutes. Counting true rows (1,047, including 1,002 useful and 45 separator lines/totals to delete). Listing of tabs (3 tabs: Marvel, DC, Indie). Checking the headers (12 columns but with free FR names: "Publisher", "Current rating", "Purchase cost", etc.). Decision: import in one go, after harmonization of the labels.

Phase 2: harmonization of wording.35 minutes. Publisher column: 8 variants reduced to 4 canonical values ​​(Marvel, DC, Image, Indie). Series Column: 12 spelling errors corrected via Find-Replace. Status Column: Conversion of 60 mixed rows (CGC notes in the Status column) to two separate columns. Source_purchase column: 5 variants reduced to 3 values ​​(eBay, Comic shop, Convention).

Phase 3: format conversion.12 minutes. Reformat the 1002 dates to ISO via TEXT. Conversion of 1,002 amounts to decimal number with separator point. Checking for the absence of residual € symbols.

Phase 4: UTF-8 CSV export.3 minutes. File → Upload → CSV. Quick check in a text editor that accents are preserved.

Phase 5: upload and MCC mapping.8 minutes. Drag and drop of the CSV. Mapping of the 12 columns (10 automatic, 2 manual: “Current quote” → Current_value and “Purchase cost” → Pay_price). Preview of the first 10 lines validated. Launch.

Phase 6: import and results.1 minute 20 seconds (effective import time). Results: 982 lines imported successfully, 12 duplicates merged (re-imports of re-editions), 8 lines rejected with errors (4 date format errors, 2 serial reference errors, 2 grade consistency errors).

Phase 7: error correction.18 minutes. Downloading the error report. Fix 8 lines in Excel. Partial re-import. All 8 lines pass on the second try.

Phase 8: checking 50 random lines.32 minutes. Generation of 50 random indices, opening of each line, verification of series, number, date, price, variant, grade. 1 error detected (a CGC grade 9.4 displayed as 9.6 due to an ambiguous entry in the source table — corrected in 30 seconds). All other fields are true to the source.

Phase 9: global checks and backup.8 minutes. Comparison of the number of records (1,002 source vs 1,002 in MCC: OK). Sum of Pay_Prices (€3,847 source vs €3,847 MCC: OK). Counting separate publishers (4 sources vs 4 MCC: OK). Export of a CSV backup from MCC, local storage + cloud + USB key.

Total timed migration:2 hours 12 minutesfor 1,000 comics. Compared to the 40+ hours it would have taken to manually re-enter a new application without importing, this is a 95% time saving. Compared to the initial entry time spread over four years (estimated at 60 hours on Sheets), this is also a net gain because the migration capitalizes on the work already done.

To assess the real value of the collection once migrated and benefit from MCC's live eBay rating, the option tofree estimategives an updated valuation range in just a few minutes. To explore the catalog of pre-wired series that now speed up future entries, seethe comics catalog. Beginner collectors who are still hesitant to invest in an app can consult thebeginner's guide to comics collector, and FR collectors during itcomics collector's guide in France.

Methodological disclaimer.The timed migration times come from a real case on a collection of 1,000 comics managed for four years on Google Sheets. Actual durations vary depending on the cleanliness of the source spreadsheet, the user's familiarity with the tools, and the complexity of particular cases (multiple copies, unlisted indie comics). Estimates of time savings are illustrations and constitute neither a guarantee of performance nor financial advice. MCC's eBay live valuation is based on comparable sold listings and reflects market estimates which may change.

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