Dummy File Generator

Continue in the tool

More pages for this tool

test file upload size limit

Test a file upload size limit: limit minus 1, limit and limit plus 1

Open Upload limit mode, enter the configured value and its unit, and download the trio. Send all three, smallest to largest, and note at which one the system flips from accepting to refusing. If the flip does not happen between the second and the third, the real limit is somewhere else.

Upload limits live in several layers

An upload crosses several layers, and each one may have its own ceiling. In nginx, the client_max_body_size directive defaults to 1m and, when exceeded, the server answers 413 Request Entity Too Large (the documentation warns that browsers do not display this error well). With a value of 0 the check is turned off. In PHP, upload_max_filesize is 2M and post_max_size is 8M when php.ini is not loaded, and post_max_size must be larger than the first; max_file_uploads caps a request at 20 files. After those come the load balancer, the CDN, the framework and the business rule.
The trio method isolates the byte. With limit L, the file of L minus 1 byte and the one of L bytes should be accepted, and the one of L plus 1 should be refused. If the L byte file is refused, the comparison uses "less than" instead of "less than or equal". If the L plus 1 file passes, the limit is higher than announced or the unit differs (MB versus MiB). If all fail, something before the limit, such as the file type or another lower ceiling in an earlier layer, is blocking the submission, and it is worth trying a very small file first.
Choose the same format as real use, because type validation usually runs before size validation. For an image field, generate PNG or JPG; for documents, PDF. The PNG requires the size to be the natural size of the image or at least 12 bytes larger, and the tool already adjusts the dimensions by itself for each size in the trio. The request body also carries multipart headers, so the total size on the wire is slightly larger than the file, and some limits count the whole body and not just the file.

Checked trios

2 MiB limit

Input: 2 MiB
Expected output: 2.097.151, 2.097.152 e 2.097.153 bytes

2 times 1,048,576, minus 1, exact and plus 1.

10 MB limit

Input: 10 MB
Expected output: 9.999.999, 10.000.000 e 10.000.001 bytes

In MiB it would be 9.54, so a MiB-based system would accept all three.

100 byte limit

Input: 100 B
Expected output: 99, 100 e 101 bytes

Useful for testing text fields and tiny files as TXT or BIN.

Zero limit

Input: 0 B
Expected output: Erro: informe um limite maior que zero

To test an empty file, generate a 0 byte TXT or BIN in One size mode.

Full tool FAQ

What is the difference between MB and MiB when generating a file?

1 MB is 1,000,000 bytes and 1 MiB is 1,048,576 bytes, a 4.86% difference. The same goes for KB (1,000) and KiB (1,024), GB (1,000,000,000) and GiB (1,073,741,824). NIST notes that memory makers often use megabyte for 1,048,576 bytes and storage makers for 1,000,000, so the tool shows the size in both systems and lets you pick the unit.

Are the files valid or do they just have the right extension?

Why do some sizes return a minimum size error?

What is the largest size I can generate?

How do I test the upload limit of a server or form?

How does the PNG reach the exact size?

Can I generate a deliberately corrupted file?

Does the WAV have the exact duration I want?

Is the CSV and JSON data real?

Do my files go to any server?

Frequently asked questions

Why do I get 413 even with the file under the application limit?

Because a proxy or server in front of the application, such as nginx with client_max_body_size at the 1m default, may block first. Raise the lowest ceiling in the chain, not just the application one.

Can I also test the maximum number of files?

Yes: generate several small files in Several sizes mode and download the ZIP, or generate one of them repeatedly. In PHP the max_file_uploads default is 20 files per request.

Does the limit count the file size or the request size?

It depends on the layer. nginx client_max_body_size looks at the request body, which includes the form multipart headers; an application limit usually looks only at the file. That is why the exact byte of the test can land slightly before or after what you expect.

Next steps

Continue in the tool

Open full tool

test file upload size limit

Test a file upload size limit: limit minus 1, limit and limit plus 1

Upload limits live in several layers

An upload crosses several layers, and each one may have its own ceiling. In nginx, the client_max_body_size directive defaults to 1m and, when exceeded, the server answers 413 Request Entity Too Large (the documentation warns that browsers do not display this error well). With a value of 0 the check is turned off. In PHP, upload_max_filesize is 2M and post_max_size is 8M when php.ini is not loaded, and post_max_size must be larger than the first; max_file_uploads caps a request at 20 files. After those come the load balancer, the CDN, the framework and the business rule.

The trio method isolates the byte. With limit L, the file of L minus 1 byte and the one of L bytes should be accepted, and the one of L plus 1 should be refused. If the L byte file is refused, the comparison uses "less than" instead of "less than or equal". If the L plus 1 file passes, the limit is higher than announced or the unit differs (MB versus MiB). If all fail, something before the limit, such as the file type or another lower ceiling in an earlier layer, is blocking the submission, and it is worth trying a very small file first.

Choose the same format as real use, because type validation usually runs before size validation. For an image field, generate PNG or JPG; for documents, PDF. The PNG requires the size to be the natural size of the image or at least 12 bytes larger, and the tool already adjusts the dimensions by itself for each size in the trio. The request body also carries multipart headers, so the total size on the wire is slightly larger than the file, and some limits count the whole body and not just the file.

Checked trios

2 MiB limit

Input: 2 MiB
Expected output: 2.097.151, 2.097.152 e 2.097.153 bytes

2 times 1,048,576, minus 1, exact and plus 1.

10 MB limit

Input: 10 MB
Expected output: 9.999.999, 10.000.000 e 10.000.001 bytes

In MiB it would be 9.54, so a MiB-based system would accept all three.

100 byte limit

Input: 100 B
Expected output: 99, 100 e 101 bytes

Useful for testing text fields and tiny files as TXT or BIN.

Zero limit

Input: 0 B
Expected output: Erro: informe um limite maior que zero

To test an empty file, generate a 0 byte TXT or BIN in One size mode.

Full tool FAQ

What is the difference between MB and MiB when generating a file?

Are the files valid or do they just have the right extension?

Why do some sizes return a minimum size error?

What is the largest size I can generate?

How do I test the upload limit of a server or form?

How does the PNG reach the exact size?

Can I generate a deliberately corrupted file?

Does the WAV have the exact duration I want?

Is the CSV and JSON data real?

Do my files go to any server?

Frequently asked questions

Why do I get 413 even with the file under the application limit?

Because a proxy or server in front of the application, such as nginx with client_max_body_size at the 1m default, may block first. Raise the lowest ceiling in the chain, not just the application one.

Can I also test the maximum number of files?

Yes: generate several small files in Several sizes mode and download the ZIP, or generate one of them repeatedly. In PHP the max_file_uploads default is 20 files per request.