Multipart Boundary Generator

Generate a reproducible multipart boundary from explicit byte values and detect collisions with supplied body text.

Description

A multipart boundary separates body parts and must avoid collisions with delimiter-like body lines.

A multipart boundary separates body parts and must avoid collisions with delimiter-like body lines. Reproducibility here comes from explicit caller-provided bytes rather than internally generated randomness.^[1]

Generate a reproducible multipart boundary from explicit byte values and detect collisions with supplied body text.

When to use Multipart Boundary Generator

Use this tool to generate a reproducible multipart boundary from explicit byte values and detect collisions with supplied body text.

Choose the URL, decoded source text, header value or explicit byte list requested by this tool. Paste the complete relevant input and follow its parsing and encoding conventions.

How to use Multipart Boundary Generator and understand its results

Choose the URL, decoded source text, header value or explicit byte list requested by this tool. Paste the complete relevant input and follow its parsing and encoding conventions.
Enter entropyBytes, body using the field table and calculation rules, then run the tool.
Read boundary, collides. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
entropyBytes	Explicit entropy bytes supplied by the caller.	list of integer; minimum: 0; maximum: 255; minimum entries: 8; maximum entries: 24	Required
body	Body text to check for boundary collisions.	string; maximum length: 1000000	Required

Supply 8–24 integers from 0–255 and the complete body text to inspect. Format each byte in two-digit hex, prefix the resulting string and scan CRLF/LF/CR-separated lines. Return the boundary and collision flag. If collides is true, supply different bytes and rerun.

boundary='toolio-'+concatenate(two-digit lowercase hex bytes); collides=any body line starts with '--'+boundary

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
boundary	ASCII multipart boundary.	string; maximum length: 1000000
collides	Whether a delimiter line containing the boundary occurs in the body.	boolean

json

{
  "input": {
    "entropyBytes": [
      1,
      35,
      69,
      103,
      137,
      171,
      205,
      239
    ],
    "body": "Content for upload"
  },
  "output": {
    "boundary": "toolio-0123456789abcdef",
    "collides": false
  }
}

Limitations and assumptions

The tool does not generate entropy or construct multipart parts. Collision checking is conservative at line starts and applies only to the supplied text, not omitted binary body content.

Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Extremely large text inputs are rejected. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.

Alternative or Complementary methods

Use Subresource Integrity Hash Generator: Hash explicit UTF-8 text with SHA-256, SHA-384, or SHA-512 and emit Base64 Subresource Integrity metadata. For a complementary task, use Integrity Attribute Parser: Split integrity metadata into supported SHA algorithm tokens, digest text, and options, reporting unsupported or malformed tokens separately.

References

Multipart Boundary Generator — tool.io

Similar or alternative tools

Subresource Integrity Hash Generator
Hash explicit UTF-8 text with SHA-256, SHA-384, or SHA-512 and emit Base64 Subresource Integrity metadata.
Integrity Attribute Parser
Split integrity metadata into supported SHA algorithm tokens, digest text, and options, reporting unsupported or malformed tokens separately.