File checks help you find the part of an upload that needs attention. You can inspect size, recognised format, available image dimensions and PDF page information, then compare supported facts with the rules supplied by the receiving website. Start here when the error is unclear or when you want to verify a prepared copy before submitting it.
Measure first, then decide whether an edit is needed
A rejected upload is not proof that the file needs conversion. The wrong account, an expired form session or an unavailable service can produce an error too. Measuring the file gives you a useful starting point: either a stated requirement does not match, or the technical conditions you checked appear to fit.
Keep the source unchanged while checking. If you immediately resize, rename and convert it, you create several possible explanations for the next result. A clear starting measurement lets you make one justified change and compare the output with the original. It also helps you explain the problem if the receiving organisation needs to investigate.
Size checks answer a storage question
File size describes how much data is stored in the selected file. It is different from the dimensions of an image or the physical size of a PDF page. An upload may impose more than one of those limits, so a size pass should not be read as a pass for the whole document.
The displayed KB or MB figure may be rounded. The underlying comparisons use file bytes, but the current maximum-MB input uses a binary MiB conversion. If a receiving site specifies decimal bytes, allow for that distinction rather than assuming the labels mean exactly the same number. A useful buffer below a hard maximum reduces boundary confusion.
Format checks look beyond a filename
A filename ending such as .jpg is a label. Recognised file signatures provide another clue about the actual format. If those disagree, investigate the source rather than changing the extension repeatedly. The right next step may be a genuine export from the application that created the file, not a cosmetic rename.
Signature recognition is limited to supported formats and is not a malware verdict. A recognised PDF header does not prove every object in the document is valid, nor does it establish that the file contains the evidence the receiver wants. Different checkers perform different levels of inspection; read the report and its stated limits.
Image dimensions describe pixels
Width and height are useful when a form asks for a minimum resolution, a maximum size or a particular shape. Multiply them to understand the total pixel count, but retain the separate width and height figures when entering a requirement. A square image and a wide banner can have similar pixel totals while fitting very different spaces.
Available measurements depend on the recognised format and inspection method. Some HEIC files do not expose usable dimensions in a read-only report. An unavailable measurement should remain unknown. It is not sensible to substitute a guessed camera resolution or assume that the image matches the dimensions of another photograph taken on the same phone.
PDF page checks answer another set of questions
A PDF can contain pages with different sizes and rotations. A page-size checker helps identify whether the file includes mixed geometry or an unexpected number of pages. It does not turn the document into a valid application pack or decide whether the printed page numbers match the receiver’s requested evidence.
Use page positions carefully. The first page in the file may be a cover with no printed number, so page three on screen may not be the sheet labelled 3. When you later extract or delete pages, verify the selection in the actual output. Readability and completeness are still visual and task-specific checks.
A compatibility report needs accurate requirements
The compatibility checkers compare supported facts with fields you supply, such as allowed formats, maximum size and image dimensions. Copy those rules from the current upload field or its official help page. Picking a destination label does not fetch an organisation’s private or account-specific rules automatically.
Only enter conditions that are actually stated. Guessing a minimum width can create a false problem; leaving an unknown rule blank accurately leaves that question unresolved. The custom-requirements page is useful when several limits must be recorded together. It should help you preserve the source of a rule, not make an invented rule sound official.
Interpret a pass, an issue and an incomplete result
A pass means no mismatch was found in the relevant supported comparisons that completed. An issue identifies something to investigate or change. An incomplete result means a required fact or rule could not be established. These outcomes tell you what was measured, rather than assigning a general quality score to the file.
For example, an image can pass a supplied size limit while its dimensions remain unavailable. Treating that as fully approved would hide the missing measurement. Conversely, an unrecognised format does not automatically mean the file is dangerous; it may simply be outside the checker’s supported set. Use the actual explanation rather than guessing from a colour or icon.
Check several files without losing track of each one
Bulk compatibility checking is useful for a small set of documents that must meet the same stated limits. Each selected file still needs its own result. A successful check on one attachment does not make a differently sized or differently formatted attachment suitable by association.
Name the files clearly before starting and compare the report with the upload fields you intend to use. If different fields have different rules, check those groups separately. A shared maximum for an entire submission is also different from a per-file cap, so do not add individual passes together and assume the combined upload is allowed.
Use the result to choose one next action
A format mismatch points towards a supported conversion. A genuine size problem may call for compression or a new source export. Incorrect image dimensions can require permitted resizing or a better original. A PDF with the wrong pages needs document organisation rather than image conversion.
After the change, check the saved output. Measurements taken before an operation do not describe the new file automatically. If the measurements already fit and the receiving form still fails, investigate its session and permissions. Repeating conversions without a new reason can damage quality and create more confusing copies.
Save the information you will need for support
If you need help from the receiving service, make a short note of the upload field, stated limit, actual format and error message. Record whether you tried the same file in a fresh signed-in session. This gives support a reproducible description without sending them several differently altered versions whose history is unclear.
Only include document contents through the organisation’s approved support process. A technical question about a size limit usually does not require attaching confidential evidence to a general message. Keep your original file available while the receiver clarifies the rule, then make any requested change deliberately.
Questions that come up
Can a checker certify that my file is safe?
No. These measurements and structural checks are not an antivirus service or a complete security review. Use trusted sources and appropriate security software for file safety. A format or dimension result answers only the technical question it actually measures.
Should I fill in every optional requirement?
Only when the receiving service provides that requirement. Empty fields are preferable to invented limits. If you need an exact rule, check the current instructions or ask the receiver. A report based on guessed requirements can be precise about the wrong task.